Display device and manufacturing method

Abstract

A display device includes a variable wavelength light emitting diode (LED) and a band-stop filter positioned between the variable wavelength LED and a light emitting surface of the display device. The variable wavelength LED includes an n-doped portion, a p-doped portion, and a light emitting region positioned between the n-doped portion and the p-doped portion, the light emitting region configured to emit light at a peak emission wavelength under an electrical bias across the region, and the variable wavelength LED configured such that the peak emission wavelength of the LED is variable over an emission wavelength range of at least 40 nanometers by varying driving conditions provided to the LED. The band-stop filter is configured to attenuate emergent light rays having wavelengths falling within a stop band wavelength range, and the band-stop filter is configured such that the stop band wavelength range is within the emission wavelength range of the variable wavelength LED. A method for manufacturing such a display device is also provided.

Description

Technical Field

[0001] This invention relates to a display device comprising a variable wavelength LED, and a method for manufacturing the display device. In particular, this invention relates to a display device comprising a variable wavelength LED and a band-stop filter. Background Technology

[0002] III-V semiconductor materials are particularly important for semiconductor device design, especially the III-nitride semiconductor family.

[0003] "III-V" semiconductors include binary, ternary, and quaternary alloys of the following two elements: group III elements such as gallium, aluminum, and indium, and group V elements such as nitrogen, phosphorus, arsenic, and antimony, and are important for many applications, including electronic and optoelectronic products.

[0004] Of particular importance are semiconductor materials commonly known as "Group III nitrides," which include gallium nitride (GaN), indium nitride (InN), and aluminum nitride (AlN), as well as their ternary and quaternary alloys. (Al,In)GaN is a term encompassing AlGaN, InGaN, and GaN. Group III nitride materials have not only achieved commercial success in solid-state lighting and power electronics, but have also demonstrated exceptional advantages in quantum light sources and light-matter interactions.

[0005] Although various group III nitride materials have commercial value, gallium nitride (GaN) is widely regarded as one of the most important novel semiconductor materials and is particularly important for many applications.

[0006] The description of this invention primarily refers to GaN and InGaN, but can be advantageously applied to alternative combinations of group III nitride materials.

[0007] It is known that introducing porosity into bulk group III nitrides such as GaN can profoundly affect their material properties (optical, mechanical, electrical, thermal, etc.). Therefore, the possibility of adjusting the wide range of material properties of GaN and group III nitride semiconductors by changing the porosity makes porous GaN important for optoelectronic applications.

[0008] The applicant, Poro Technologies Ltd, has developed variable-wavelength LEDs formed from group III nitride semiconductor materials grown on porous regions of group III nitride materials, representing a significant improvement over conventional three-color LED displays. These variable-wavelength LEDs can emit a broad spectrum of different emission wavelengths in response to varying driving conditions provided to them, rather than emitting a single color as with conventional LEDs. These variable-wavelength LEDs and their manufacturing methods are disclosed in International Patent Application No. PCT / GB2022 / 051997, published as World Patent No. WO2023 / 007174.

[0009] Because the peak emission wavelength of such variable-wavelength LEDs can be adjusted by changing the driving conditions, a single variable-wavelength LED can replace multiple "monochrome" subpixels. In several particularly preferred embodiments, by adjusting the driving conditions provided to the LED, the same variable-wavelength LED can be adjusted to emit any of red, green, or blue light. This means that a color display can be formed from an array of variable-wavelength LEDs, where each variable-wavelength LED acts as a color-variable pixel, or alternatively, as a color-variable subpixel in a subpixelated display.

[0010] In ProTech's Dynamic Pixel Adjustment (DPT®) variable wavelength LEDs, the peak emission wavelength of the variable wavelength LED is strongly dependent on the magnitude of the electronic drive signal supplied to a given LED, and longer wavelength emission colors require lower drive current / voltage, which inherently produces lower luminance. Consequently, the full width at half maximum (FWHM) spectral width of the emission peak emitted by such variable wavelength LEDs is typically wider than that of conventional "monochrome" LEDs. This presents a challenge because the emission spectra emitted by variable wavelength LEDs may overlap in different operating modes, which can reduce the purity of the desired emitted color, causing the "observed" dominant wavelength to deviate from the expected spectral peak wavelength and reducing the size of the color gamut that the display device can display.

[0011] As is well known, to improve the color purity of a monochrome LED, a spectral element centered on the LED's single emission color, such as a bandpass filter or a distributed Briggs reflector (DBR), can be added to narrow the FWHM of the LED's emission peak. Another solution is to use a color filter to block emitted colors other than the color of interest. However, both solutions are only effective in configurations that use spatially separated sub-pixels to emit discrete primary emission wavelengths. These methods are not suitable for displays that emit multiple different primary emission wavelengths from the same LED, because the spectral element that narrows the emission peak of the primary emission wavelength will block the emission of other primary emission wavelengths from the same LED.

[0012] Besides being unsuitable for displays where multiple colors are emitted from the same pixel or subpixel, existing solutions have various drawbacks. A different color filter is required above each pixel or subpixel, introducing additional processing steps and increasing complexity and cost. Furthermore, spectral filters made of quantum dots or other phosphor materials typically have low conversion efficiency, poor material stability, and short lifespan. These materials also inherently limit response times and can cause blurry images in mobile systems, making them unsuitable for high-resolution, high-refresh-rate display devices. Summary of the Invention

[0013] This application relates to a display device comprising variable wavelength light-emitting diodes (LEDs), and a method for manufacturing the display device. The display device preferably comprises a plurality of such variable wavelength LEDs, such as an array of variable wavelength micro LEDs.

[0014] This invention is defined in the independent claim of the patent, which should be referred to therein. Preferred or advantageous features of this invention are defined in the dependent claims appended to the patent.

[0015] Display device

[0016] In a first aspect of the present invention, a display device is provided, comprising:

[0017] A variable wavelength light-emitting diode (LED); and a band-stop filter located between the variable wavelength LED and the light-emitting surface of the display device.

[0018] The variable wavelength LED includes an n-doped portion, a p-doped portion, and a light-emitting region located between the n-doped portion and the p-doped portion. The light-emitting region is configured to emit light at a peak emission wavelength under an electrical bias voltage across it. The variable wavelength LED is configured such that the peak emission wavelength of the LED can be varied within an emission wavelength range of at least 40 nanometers by changing the driving conditions provided to the LED by the power supply.

[0019] The bandstop filter is configured to attenuate emitted light with wavelengths falling within the bandstop wavelength range; the bandstop filter is configured such that the bandstop wavelength range is within the emission wavelength range of the variable wavelength LED.

[0020] Also known as a band rejection filter, a band-stop filter is an optical filter that allows most wavelengths of light to transmit without alteration, but attenuates wavelengths within the filter's stopband to very low levels. This type of optical band-stop filter can use scattering or destructive interference as needed to attenuate wavelengths within the stopband.

[0021] The bandstop filter is located between the variable wavelength LED and the light-emitting surface of the display device, causing light emitted from the variable wavelength LED to pass through the bandstop filter before exiting the light-emitting surface of the display device. The light-emitting surface of the display device may include an outlet through which light exits the display device, causing the bandstop filter to be located between the variable wavelength LED and the outlet of the display device.

[0022] Because the stopband of the bandstop filter is within the emission wavelength range of the variable wavelength LED, the bandstop filter is configured to attenuate a portion of the wavelength emitted by the variable wavelength LED. By selecting a bandstop filter with a stopband covering a specific wavelength range, the bandstop filter can be used to attenuate or block a portion of one or more emission peaks emitted by the variable wavelength LED.

[0023] The light-emitting regions are configured to emit light at the peak emission wavelength under a bias voltage across them. However, due to the inherent emission characteristics of the variable wavelength LED, the LED emits an emission spectrum with a spectral width centered on the peak emission wavelength and also including wavelengths above and below the peak emission wavelength. The spectral width of any emission peak can be defined by its FWHM (Frequency Wavelength Mean).

[0024] Compared to conventional monochrome LEDs, the variable wavelength LEDs used in this invention can emit a peak emission wavelength with a wider FWHM. By including a band-stop filter in the display device, and selecting a band-stop filter that covers a portion of the emission wavelength range of the variable wavelength LED, the emission wavelength emitted from the display device can be narrowed. By using a band-stop to block a portion of the wavelength emitted by the LED, the width of the emission peak transmitted from the display device can be effectively narrowed, thereby improving the color purity achievable with variable wavelength LEDs.

[0025] In the prior art, bandpass filters have been used to artificially narrow the emission peaks separating LED sub-pixels. Bandpass filters allow transmission of wavelengths within a narrow range in the passband while blocking all other wavelengths. In this invention, a bandstop filter is used instead of a bandpass filter. The bandstop filter operates in the opposite way to a bandpass filter, blocking transmission of wavelengths within a relatively narrow range in the stopband while allowing transmission of all wavelengths outside the stopband.

[0026] The display device is preferably configured such that the variable wavelength LED can operate in a plurality of discrete emission modes by providing a plurality of discrete driving conditions to the LED. The variable wavelength LED emits different peak emission wavelengths in each discrete emission mode, and each emission mode produces its own emission mode spectrum, which includes wavelengths around the peak emission wavelength.

[0027] The variable wavelength LED is preferably driven to emit light at a first peak emission wavelength in response to a first electrical driving condition provided to the variable wavelength LED. The variable wavelength LED is also preferably driven to emit light at a second peak emission wavelength in response to a second electrical driving condition. Both the first and second peak emission wavelengths are within the emission wavelength range of the variable wavelength LED.

[0028] The bandstop filter is preferably configured to attenuate emitted wavelengths within a stopband located between the first peak emission wavelength and the second peak emission wavelength. The stopband wavelength range is preferably positioned between the first peak emission wavelength and the second peak emission wavelength to attenuate overlapping emitted wavelengths emitted in both the first and second modes. By attenuating the emitted wavelengths between the first and second peak emission wavelengths, the bandstop filter advantageously eliminates color overlap between these two emission peaks, thereby improving the purity of colors emitted in both modes. This effectively reduces the FWHM of both the first and second peak emission wavelengths and expands the color gamut that can be displayed by the display device.

[0029] The display device preferably includes one or more bandstop filters located between the variable wavelength LED and the light-emitting surface of the device, each bandstop filter being configured to block the transmission of emitted wavelengths within a stopband.

[0030] Using one or more bandstop filters can advantageously block transmission of certain stopband wavelengths from the display device, thereby narrowing the FWHM of those emission peaks, while still allowing transmission of all other wavelengths emitted by the variable wavelength LED. This bandstop filter is particularly suitable for use with variable wavelength LEDs when driving the same variable wavelength LED to emit multiple discrete emission peaks.

[0031] The variable wavelength LED embodiment that can be used in the present invention is called Dynamic Pixel Adjustment (DPT®) Variable Wavelength LED from ProTech Corporation, and is disclosed in International Patent Application No. PCT / GB2022 / 051997, which is published as World Patent No. WO2023 / 007174.

[0032] Although a continuous spectrum of different emission wavelengths can be directly emitted from a variable wavelength LED by changing the driving conditions supplied to the LED, additional chromaticity can be displayed by driving the LED to emit multiple "primary color" wavelengths, resulting in the overall output signal observed by the observer being a temporal combination of the emitted primary colors.

[0033] In a subpixelated display, different primary color emission wavelengths can be emitted by separate subpixels. All of these subpixels can be variable wavelength LEDs, or some subpixels can be non-variable wavelength LEDs.

[0034] In a preferred embodiment, the display device is a subpixelated display, wherein the variable wavelength LED is a first subpixel that can be driven to emit light at a first peak emission wavelength in response to a first driving condition provided to the first subpixel, and wherein the display includes a second LED subpixel that can be driven to emit light at a second peak emission wavelength in response to a second driving condition provided to the second subpixel. The second LED subpixel is preferably a second variable wavelength LED subpixel. In this embodiment, the first and second subpixels are subpixels of a display pixel, and the first and second subpixels can be driven independently of each other.

[0035] In several sub-pixelated embodiments of the display device, since the sub-pixels are adjacent to each other, the light emitted by the sub-pixels at the first and second peak emission wavelengths combines to form the output chromaticity and output luminous intensity L. O The output signal. An observer viewing the display device will only perceive a single output signal from the subpixelated pixels within the display frame, and this perceived output signal will have a single output chromaticity and luminous intensity, which are the time-averaged values ​​of the emission wavelengths emitted by the variable wavelength LED subpixels.

[0036] In another preferred embodiment, the variable wavelength LED is a pixel of the device, and the display device is a field-sequential display. In this embodiment, the same variable wavelength LED pixel is driven to emit a plurality of discrete peak emission wavelengths by driving a plurality of LED pixels with different driving conditions. The variable wavelength LED can be driven to emit light at a first peak emission wavelength in response to a first electrical driving condition provided to the variable wavelength LED, and can also be driven to emit light at a second peak emission wavelength in response to a second electrical driving condition provided to the variable wavelength LED.

[0037] In a sequential display, by supplying different driving conditions to LEDs in sequential subframes of the display frame, the same variable-wavelength LED can be controlled to emit multiple discrete peak emission wavelengths. In this way, the same variable-wavelength LED can emit multiple pixels of selected "primary color emission wavelengths" one after another within the duration of a single display frame.

[0038] In use, it is preferable to drive the variable wavelength LED of the display device to emit light alternately at the first peak emission wavelength and the second peak emission wavelength by changing the driving conditions provided to the variable wavelength LED.

[0039] Ideally, the display device should be driven using field sequence control, such that the same variable-wavelength LEDs emit first and second peak emission wavelengths during discrete sub-frames within a single display frame. In other words, the same LEDs emit the first and second peak emission wavelengths one after another within a short time frame (display frame). The combination of light emitted at these first and second peak emission wavelengths forms the output chromaticity and output luminous intensity L. O The output signal. An observer viewing the display device will only perceive a single output signal from the variable wavelength LED within the display frame, and this perceived output signal will have a single output chromaticity and luminous intensity, which are the time-averaged values ​​of the emission wavelengths emitted by the variable wavelength LED in a field-sequential manner.

[0040] The bandstop filter is preferably configured to attenuate or block all emitted light rays with wavelengths falling within the stopband of the bandstop filter.

[0041] This bandstop filter is designed to block wavelengths within the stopband by either absorption or transmission.

[0042] The stopband wavelength range is narrower than the emission wavelength range of the variable wavelength LED, such that the emitted wavelengths outside the stopband within the emission wavelength range are not attenuated by the stopband filter. The stopband is thus configured to cover only a portion of the emission wavelength range of the variable wavelength LED.

[0043] The bandstop filter is preferably configured such that the bandstop wavelength range attenuates a portion of the emission wavelength range of the variable wavelength LED, but transmits shorter emission wavelengths below the bandstop wavelength range and longer emission wavelengths above the bandstop wavelength range.

[0044] Discrete transmission mode

[0045] In a preferred embodiment, the display device is configured to enable the variable wavelength LED to operate in a plurality of discrete emission modes by providing a plurality of discrete driving conditions to the LED, wherein the variable wavelength LED emits different peak emission wavelengths in each discrete emission mode, and wherein each emission mode produces an emission mode spectrum containing wavelengths around the peak emission wavelength.

[0046] The bandstop filter can be configured such that the stopband is located between the peak emission wavelengths of the discrete emission modes, thereby attenuating wavelengths between these peak emission wavelengths. Preferably, the bandstop filter can be configured to attenuate emitted wavelengths within stopbands located between the peak emission wavelengths of different emission modes.

[0047] The bandstop filter is preferably configured to attenuate the wavelengths of emitted light emitted in multiple emission modes within an overlapping range. This differs significantly from prior art, which typically employs a transmission band centered on the peak color position. Instead, this invention blocks the spectral regions between emission peaks that separate emission modes, rather than targeting a single emission peak with a transmission band.

[0048] By attenuating the emitted wavelengths that fall within the overlap of discrete emission peaks in discrete emission modes, this bandstop filter advantageously eliminates color overlap between two emission peaks, improving the purity of colors emitted in both modes. This effectively reduces the FWHM of the emission peaks on either side of the stopband and expands the color gamut that can be displayed by the display device.

[0049] The band-stop filter thus reduces the spectral power on one side of the primary color emission peak (the peak emission wavelength emitted by one emission mode of the display device).

[0050] Ideally, field sequence control should be used to control the device, thereby controlling the variable wavelength LED to operate in different emission modes in different display subframes.

[0051] In a preferred embodiment, for example, the variable wavelength LED can be driven in a first mode emitting light at a first peak emission wavelength in response to a first electrical driving condition provided to the variable wavelength LED, and can also be driven in a second mode emitting light at a second peak emission wavelength in response to a second electrical driving condition. Both the first and second peak emission wavelengths are within the emission wavelength range of the variable wavelength LED.

[0052] When the variable wavelength LED operates in the first mode, it emits a first emission mode spectrum, which is the range of emitted wavelengths centered on the first peak emission wavelength and encompassing any side of that first peak emission wavelength. When the variable wavelength LED operates in the second mode, it emits a second emission mode spectrum, which is the range of emitted wavelengths centered on the second peak emission wavelength and encompassing any side of that second peak emission wavelength. The first and second emission mode spectra overlap within an overlap range, which is the wavelength range in which both the first and second emission mode spectra have an intensity greater than zero.

[0053] In a preferred embodiment, the bandstop filter can be configured to block emitted wavelengths within a bandstop wavelength range located between the first peak emission wavelength and the second peak emission wavelength. The bandstop wavelength range is preferably located between the first peak emission wavelength and the second peak emission wavelength to attenuate the overlapping emission wavelengths emitted by the variable wavelength LED in the first and second modes.

[0054] The bandstop filter is preferably configured to attenuate the emitted wavelengths in the first and second modes within the spectral overlap range.

[0055] The bandstop filter can be configured such that the stopband does not contain any peak emission wavelengths generated by such discrete emission modes.

[0056] Alternatively, one or more of the peak emission wavelengths generated by the discrete emission modes may be located within the stopband, while another portion of the emission mode spectrum generated by the emission mode is not within the stopband.

[0057] In a preferred embodiment, the first peak emission wavelength is below 570 nm and the second peak emission wavelength is above 610 nm, causing the LED to emit green light in response to the first driving condition and red light in response to the second driving condition. The stopband of the bandstop filter is configured to attenuate wavelengths between the first and second peak emission wavelengths. By positioning the stopband between the first and second peak emission wavelengths, the green and red emission peaks are effectively narrowed, and spectral overlap between the green and red emission peaks is blocked.

[0058] The bandstop filter can be configured to attenuate wavelengths within a plurality of bandstop wavelength ranges located within the emission wavelength range of the variable wavelength LED. The bandstop filter can be configured to have multiple bandstops within the emission wavelength range of the variable wavelength LED.

[0059] Alternatively, the display device may include a plurality of bandstop filters with discrete stopband wavelength ranges within the emission wavelength range of the variable wavelength LED. These bandstop filters may be configured to attenuate the emitted wavelength within the stopband of the respective variable wavelength LED emission wavelength range. The plurality of bandstop filters are preferably located between the variable wavelength LED and the light-emitting surface of the display device, such that light emitted from the variable wavelength LED must pass through the plurality of bandstop filters before exiting the device. The plurality of bandstop filters may be stacked between the variable wavelength LED and the light-emitting surface of the display device, such that light emitted from the variable wavelength LED must pass through all of the bandstop filters before exiting the device.

[0060] By using a bandstop filter that attenuates the wavelength in multiple stopbands, or by using multiple bandstop filters with multiple individual stopbands, it is possible to narrow the multiple emission peaks of the variable wavelength LED.

[0061] 3 launch modes

[0062] In a preferred embodiment, the variable wavelength LED can be controlled to emit three discrete peak emission wavelengths by providing the LED with driving conditions that change between three discrete emission modes.

[0063] Preferably, the variable wavelength LED can be controlled to be in a first mode emitting at a first peak emission wavelength in response to a first driving condition provided by the power supply, in a second mode emitting at a second peak emission wavelength in response to a second driving condition provided by the power supply, and in a third mode emitting at a third peak emission wavelength in response to a third driving condition provided by the power supply.

[0064] The bandstop filter is preferably configured to attenuate the emitted wavelength in a first stopband located between the first and second peak emission wavelengths, and the emitted wavelength in a second stopband located between the second and third peak emission wavelengths.

[0065] Particularly preferably, the bandstop filters are configured such that the bandstops attenuate overlapping wavelengths emitted in the first and second modes, and the device preferably includes a bandstop filter having a second bandstop configured to attenuate overlapping wavelengths emitted in the second and third modes. The display device may include a single filter with two discrete bandstops, or two bandstop filters, each with one bandstop.

[0066] In a particularly preferred embodiment, the LED can be controlled to emit a blue peak emission wavelength in response to a first driving condition provided by the power supply, a green peak emission wavelength in response to a second driving condition provided by the power supply, and a red peak emission wavelength in response to a third driving condition provided by the power supply. For example, the LED can be controlled to emit a first peak emission wavelength in the range of 400-500 nanometers in response to the first driving condition provided by the power supply, a second peak emission wavelength in the range of 500-560 nanometers in response to the second driving condition provided by the power supply, and a third peak emission wavelength greater than 600 nanometers in response to the third driving condition provided by the power supply.

[0067] The function of this bandstop filter is to reduce the spectral power on one side of the selected "primary color" peak emission wavelength. For example, the bandstop filter may have a stopband selected to reduce the spectral power on the green side of the blue emission peak or on the blue side of the green emission peak. Unlike prior art bandpass filters, the stopband of this bandstop filter targets the spectral region between the primary color emission peaks, rather than the primary color emission peaks themselves. The advantage of this configuration compared to other configurations is that it is effective regardless of the color (emission mode) emitted by the variable wavelength LED: a bandstop filter with a stopband in blue or green does not affect red emission, and a bandstop filter with a stopband in green or red does not affect blue emission.

[0068] The LED can be controlled to emit a first peak emission wavelength in the range of 430-470 nm in response to a first driving condition provided by the power supply, a second peak emission wavelength in the range of 510-560 nm in response to a second driving condition provided by the power supply, and a third peak emission wavelength in the range of 600-660 nm in response to a third driving condition provided by the power supply.

[0069] The first, second, and third driving conditions are preferably first, second, and third driving currents with different values ​​corresponding to the first, second, and third current densities. Alternatively, the first, second, and third driving conditions can be first, second, and third driving voltages with different values.

[0070] Band-stop filter

[0071] This bandstop filter is an optical bandstop filter that can attenuate wavelengths within the stopband using scattering or destructive interference as needed. Various optical bandstop filters are known in the field of optics, and various such filters can be used in this invention.

[0072] This bandstop filter can be an optical notch filter, which is a bandstop filter with a narrow stopband and a high Q factor.

[0073] The bandstop filter can be selected to provide high attenuation (low transmission) within the bandstop, combined with high transmission outside the bandstop. With conventional dielectric bandstop filters, for example, it should be possible to achieve more than 90% transmission outside the bandstop and less than 10% transmission within the bandstop.

[0074] The bandstop filter may have a stop band width of at least 10 nanometers, or at least 20 nanometers, or at least 25 nanometers, or at least 30 nanometers. The bandstop filter may also have a stop band width of less than 75 nanometers, or less than 60 nanometers, or less than 50 nanometers.

[0075] The bandstop filter can be made of crystalline semiconductor or insulating material. For example, the bandstop filter can be formed of conventional dielectric material.

[0076] The bandstop filter may comprise one or more layers of porous group III nitride semiconductor material. For example, the bandstop filter may comprise a layered structure in which a plurality of first layers with a first refractive index alternate with a plurality of second layers with a second refractive index different from the first refractive index. The bandstop filter may comprise a layered structure in which a plurality of porous group III nitride semiconductor material layers alternate with a plurality of non-porous group III nitride material layers, or in which a plurality of porous group III nitride material layers with a first porosity and a first refractive index alternate with a plurality of porous group III nitride material layers with a second porosity and a second refractive index different from the first refractive index. The bandstop filter may comprise distributed Breguet reflectors (DBRs) configured to reflect wavelengths within the bandstop, thereby blocking their transmission. The thicknesses of the layers in the bandstop filter are preferably configured to attenuate wavelengths within the bandstop using destructive interference.

[0077] The bandstop filter may comprise a rulegate filter, also known as an index gradient filter. In a rulegate filter, the refractive index varies slowly throughout the structure, rather than having two alternating layers with a fixed refractive index. The rulegate filter may comprise one or more porous group III nitride semiconductor material layers, wherein the porosity of the porous layer varies with the layer thickness, causing the refractive index of the porous layer to vary with the layer thickness.

[0078] The bandstop filter can be configured as a bistimulus bandstop filter, which is configured to attenuate the emitted wavelength in two separate stopbands. For example, the bandstop filter can be configured to attenuate the transmitted wavelength in a first stopband located between the blue peak emission wavelength and the green peak emission wavelength, and the transmitted wavelength in a second stopband located between the green peak emission wavelength and the red peak emission wavelength.

[0079] LED array

[0080] The display device preferably includes a plurality of variable-wavelength LEDs, each configured to receive its own power supply, such as an array of variable-wavelength LEDs. Preferably, each of the plurality of LEDs is controllable such that the peak emission wavelength of each LED can be controlled by changing the driving conditions supplied to it.

[0081] The device is preferably configured such that light emitted from each of the variable wavelength LEDs passes through a bandstop filter before exiting the device. The device can be configured such that light emitted from the plurality of variable wavelength LEDs passes through the same bandstop filter (or several bandstop filters) before exiting the emitting surface of the display device. For example, the bandstop filter or filters can be configured to extend above the plurality of or all of the variable wavelength LEDs in the display, such that light emitted from the plurality of variable wavelength LEDs passes through the same bandstop filter (or several bandstop filters) before being transmitted from the emitting surface of the display device.

[0082] The display device preferably includes control electronics configured to provide adjustable drive current to the plurality of variable wavelength LEDs.

[0083] Variable wavelength LED

[0084] The variable wavelength LEDs are configured to emit a variable peak emission wavelength in response to changes in the electrical driving conditions (driving current or driving voltage) supplied to the LED. The peak emission wavelength of the LED is preferably continuously controllable within an emission wavelength range of at least 40 nanometers by changing the driving current supplied to the LED. The peak emission wavelength is preferably variable within an emission wavelength range of at least 50 nanometers, or at least 60 nanometers, or at least 70 nanometers, or at least 80 nanometers by changing the driving current, and more preferably within a range of 100 nanometers, or 110 nanometers, or 120 nanometers, or 140 nanometers, or 160 nanometers, or 180 nanometers, or 200 nanometers, or 400 nanometers, or 450 nanometers.

[0085] In a particularly preferred embodiment, the display device includes a plurality of variable wavelength LEDs, each having the same variable wavelength LED epitaxial structure, such that each variable wavelength LED in the display device is a separate variable wavelength LED, which is configured to emit a variable peak emission wavelength in response to changes in the driving conditions provided to the LED. By individually driving these variable wavelength LED pixels through driver circuitry, it is advantageous to individually adjust the emission wavelength of each pixel by providing different drive currents to these variable wavelength LED pixels.

[0086] The display is preferably connected to a driver circuit configured to supply variable value drive current or variable value drive voltage to each variable wavelength LED pixel to change the peak emission wavelength of the variable wavelength LED.

[0087] The variable wavelength light-emitting diode (LED) that can be used in the display device preferably includes:

[0088] n-doped portion;

[0089] p-doped portion;

[0090] The light-emitting region is located between the n-doped portion and the p-doped portion, and the light-emitting region contains a light-emitting layer that emits light at a peak emission wavelength under an electrical bias voltage across it;

[0091] The LED is configured to receive a power supply, wherein the peak emission wavelength of the LED is continuously controllable within the emission wavelength range by changing or controlling the driving conditions provided to the variable wavelength LED. Preferably, the peak emission wavelength of the variable wavelength LED is continuously controllable or continuously variable within an emission wavelength range of at least 40 nanometers by changing or controlling the power supply.

[0092] Since the peak emission wavelength of this variable wavelength LED is controllable or variable within the emission wavelength range, the LED can be described as a variable wavelength LED.

[0093] The variable wavelength emission behavior of this LED structure is enabled by the fact that the LED structure (n-doped portion, emitting region, and p-doped portion) is grown on a template containing porous regions. The inventors have discovered that the porous regions of the group III nitride material in the template structure prior to overgrowing the LED structure lead to higher quality crystal growth, resulting in significant benefits, including the possibility of altering the emission wavelength of the emitting region. The mechanism by which the porous regions enable the LED to emit variable wavelengths is an ongoing research topic. The benefits provided to the LED by the porous regions include strain relaxation, lattice parameter amplification, reduced wafer warping, and reduced mechanical and thermal effects during the high-temperature growth of the emitting region.

[0094] The variable wavelength LED is configured to receive power supply or drive current from a power source or LED driver. The term "drive conditions" is used here to refer to the power, current, or voltage provided to drive the LED during use.

[0095] The peak emission wavelength of the LED is preferably continuously controllable or continuously variable within the emission wavelength range by changing or controlling the amount of drive current supplied to the variable wavelength LED.

[0096] In conventional LED devices, variations in the driving current supplied to the LED produce a small shift in the emission wavelength. However, the inventors have discovered that the wavelength shift can be broadened and controlled to a greater extent compared to conventional LED materials. The LED of this invention can be controlled to emit over a much wider emission range, for example, at least 40 nanometers, rather than the limited nanometer emission range of prior art devices. Because the LED of this invention can be adjusted to emit over a wide wavelength range, it can be called a variable wavelength LED.

[0097] The LED can be a dynamically color-tunable LED, wherein the peak emission wavelength of the LED can be adjusted by changing the driving conditions supplied to the LED. These driving conditions are preferably supplied to the LED or individual variable wavelength LEDs in the display device using a drive circuit connected to a power supply.

[0098] Ideally, the LED can be driven to emit at a single peak emission wavelength in response to stable driving conditions, but at different peak emission wavelengths in response to variations in the power supply. Therefore, the LED can be used to emit a specific color for an extended period, or alternatively, by providing varying driving conditions, the LED can be driven to emit a variety of different wavelengths.

[0099] Preferably, the n-doped portion, the p-doped portion, and the luminescent region all contain or are composed of group III nitride materials, preferably GaN, InGaN, AlGaN, or AlInGaN.

[0100] The variable wavelength LED preferably comprises a single epitaxially grown diode structure including the n-doped portion, the p-doped portion, and the light-emitting region. Therefore, the variable peak emission wavelength of the LED is emitted entirely by the same LED diode structure and components.

[0101] The LED preferably comprises a porous region of group III nitride material. The light-emitting region of the LED is preferably formed above the porous region of group III nitride material. In some embodiments, either the n-doped portion or the p-doped portion may comprise a porous region of group III nitride material. In other embodiments, the n-doped portion, the p-doped portion, and the light-emitting region are provided on a substrate comprising a porous region of group III nitride material. It is preferable that the light-emitting region be overgrown after the porous region has been formed during the epitaxial growth of the LED.

[0102] The inventors have discovered that porous regions of group III nitride materials enable LEDs to emit within a peak emission wavelength range, rather than at a specific wavelength. By changing the power supply provided to the LED, the peak emission wavelength of the LED can be varied within the emission wavelength range. The present invention therefore provides a variable wavelength LED that can be controlled to emit at any wavelength within a continuous emission wavelength range. By changing the driving conditions provided to the LED by the power supply, the LED can emit at any wavelength within the LED's emission wavelength range, and not just at discrete peak emission wavelengths.

[0103] The inventors have discovered that by incorporating porous regions of group III nitride semiconductor material into the LED structure, or by forming the LED diode structure above porous regions of group III nitride semiconductor material, the LED can emit at tunable wavelengths over a wide emission range. The benefits provided to the LED by the porous regions include strain relaxation, lattice parameter amplification, reduced wafer bending, and beneficial mechanical and thermal effects during the high-temperature growth of the light-emitting region.

[0104] The light-emitting region of the LED is preferably formed over a porous region of a group III nitride material during manufacturing, such that the porous region influences the structure and mechanical properties of the semiconductor layer epitaxially deposited over the porous region. The semiconductor material layer deposited over the porous region during growth experiences benefits such as strain relaxation, lattice parameter amplification, and reduced wafer bending, thereby imparting benefits to the LED light-emitting region and influencing its structure and luminescence behavior.

[0105] Once the LED (active) light-emitting region has been epitaxially grown over the porous region, and the effect of the porous region has enhanced the quality of the active region, the beneficial effects of the porous region on the emission properties are permanently imparted to the LED active region. Therefore, the LED diode structure can remain on the porous region, in which case the variable wavelength LED contains a porous region of group III nitride material, or alternatively, the porous region can be removed from the LED structure during the fabrication of the LED into a device after epitaxial growth.

[0106] The width of the emission wavelength range can vary depending on the structure and composition of the LED structure (n-doped portion, light-emitting region, and p-doped portion) and the structure and porosity of the porous region. The width of the emission wavelength range can also vary depending on the size and shape of the LED (pixel size and shape).

[0107] In several preferred embodiments, by changing the power supply, the peak emission wavelength can be controlled within an emission wavelength range of at least 40 nm, or at least 50 nm, or at least 60 nm, or at least 70 nm, or at least 80 nm. Preferably, the peak emission wavelength can be controlled within an emission wavelength range reaching 100 nm, or 110 nm, or 120 nm, or 130 nm, or 140 nm, or 150 nm, or 160 nm, or 170 nm, or 180 nm, or 190 nm, or 200 nm, or 400 nm, or 450 nm. Therefore, the emission wavelength range achievable with the LED of the present invention is significantly larger than the emission range achievable with prior art LEDs.

[0108] Advantageously, the variable wavelength LED can be controlled to emit at any peak emission wavelength within its emission wavelength range. By changing the characteristics of the power supply and the size and shape of the LED pixels, the variable wavelength LED can be controlled to emit light at any selected peak emission wavelength within this range.

[0109] The emission wavelength of the variable wavelength LED is preferably continuously variable within its emission wavelength range in response to the driving conditions provided by a power supply that is continuously varied within the range of driving conditions.

[0110] The position of this emission wavelength range in the electromagnetic spectrum can also vary depending on the design of the variable wavelength LED structure (n-doped portion, emitting region, and p-doped portion). For example, the wavelengths included in this emission wavelength range can depend on the number and composition of the emitting layers in the variable wavelength LED. It is known in the art that a large number of various LED active regions are used to emit at different wavelengths in the visible spectrum; therefore, by using the emitting regions of the LED of the present invention, which form different emitting regions, an emission wavelength range covering different parts of the spectrum can be obtained.

[0111] The variable wavelength LED can emit wavelengths between 400 nm and 850 nm, or between 400 nm and 800 nm, or between 400 nm and 690 nm, or between 400 nm and 675 nm. This emission wavelength range can be a sub-range within the 400 nm to 750 nm range. By selecting different LED active areas and controlling the size and shape of the LED pixels, the emission wavelength range can be adjusted to cover any part of this range.

[0112] Preferably, the emission wavelength range of the variable wavelength LED extends from a lower end of less than 410 nm, or 430 nm, or 450 nm, or 470 nm, or 500 nm, or 520 nm, or 540 nm, or 560 nm to an upper end of more than 570 nm, or 580 nm, or 600 nm, or 610 nm, or 630 nm, or 650 nm, or 675 nm. As mentioned above, the first and second ends of the emission wavelength range can be adjusted depending on the choice of LED structure, LED shape, and size.

[0113] For example, in several preferred embodiments, the lower end of the emission wavelength may be between 400 nm and 450 nm (purple), or between 450 nm and 500 nm (blue), or between 500 nm and 570 nm (green), and the upper end of the emission wavelength may be between 570 nm and 590 nm (yellow), or between 590 nm and 610 nm (orange), or between 610 nm and 700 nm (red).

[0114] In a preferred embodiment, the variable wavelength LED emission wavelength range can extend from below 500 nm to above 610 nm, allowing the peak emission wavelength of the LED to be changed to any wavelength from blue (below 500 nm) to red (above 610 nm) by altering the driving conditions provided to the variable wavelength LED. Providing a single LED design that can be controlled to emit at blue wavelengths (450-500 nm), green (500-570 nm), and also at yellow (570-590 nm), orange (590-610 nm), and red (610-760 nm) is highly advantageous and offers significant advantages for LED displays.

[0115] In other preferred embodiments, by changing the driving conditions provided to the variable wavelength LED, the emission wavelength range of the variable wavelength LED can be extended between 520 nm and 660 nm, or between 550 nm and 650 nm.

[0116] In a particularly preferred embodiment, the peak emission wavelength can be controlled between 540 nm and 680 nm, or between 560 nm and 675 nm, by changing the driving conditions provided to the variable wavelength LED. Therefore, the same LED can be controlled to emit at any peak emission wavelength between 540 nm for green and 680 nm for red. Historically, green and red LEDs have been more difficult to manufacture than shorter wavelength blue LEDs due to issues such as the difficulty in incorporating the required indium content into the emitting region. Therefore, providing a single LED design that can be controlled to emit at a green wavelength (500-570 nm) and also at yellow (570-590 nm), orange (590-610 nm), and red (610-760 nm) wavelengths is highly advantageous and offers significant advantages for LED displays.

[0117] In another preferred embodiment, the peak emission wavelength can be controlled between 520 nm and 675 nm, or between 550 nm and 650 nm, by changing the driving conditions provided to the variable wavelength LED.

[0118] Although the variable wavelength LED can emit within a continuous range of emission wavelengths, in some specific embodiments it may be necessary to control the LED to operate in multiple discrete emission modes, for example, in response to a power supply with multiple drive modes. For example, by driving the LED in multiple different modes corresponding to discrete emission colors, a simplified color display can be provided, wherein the discrete emission colors are mixed using known methods to give the desired visual effect.

[0119] Preferably, the variable wavelength LED can be controlled to emit at least two discrete peak emission wavelengths by changing the driving conditions supplied by the power supply between two discrete driving conditions (e.g., two discrete values ​​of driving current). The LED can be controlled to emit at a first peak emission wavelength in response to a first driving condition supplied by the power supply (which may be a driving current with a first value), and to emit at a second peak emission wavelength in response to a second driving condition supplied by the power supply (which may be a driving current with a second value different from the first value).

[0120] Ideally, the variable wavelength LED should be controllable to emit at least three discrete peak emission wavelengths by changing the driving conditions provided by the power supply. Therefore, the peak emission wavelength of the variable wavelength LED is variable within at least three "colors" of the EM spectrum.

[0121] The variable wavelength LED can be controlled to emit at a first peak emission wavelength in response to a first driving condition provided by the power supply, emit at a second peak emission wavelength in response to a second driving condition provided by the power supply, and emit at a third peak emission wavelength in response to a third driving condition provided by the power supply.

[0122] Ideally, the variable wavelength LED can be controlled to emit at a blue peak emission wavelength in response to a first driving condition provided by the power supply, at a green peak emission wavelength in response to a second driving condition provided by the power supply, and at a red peak emission wavelength in response to a third driving condition provided by the power supply.

[0123] The variable wavelength LED can be controlled to emit at a first peak emission wavelength in the range of 400-500 nm in response to a first driving condition provided by the power supply, at a second peak emission wavelength in the range of 500-550 nm in response to a second driving condition provided by the power supply, and at a third peak emission wavelength greater than 600 nm in response to a third driving condition provided by the power supply.

[0124] Preferably, the variable wavelength LED can be controlled to emit a first peak emission wavelength in the range of 430-460 nm in response to a first driving condition provided by the power supply, a second peak emission wavelength in the range of 510-560 nm in response to a second driving condition provided by the power supply, and a third peak emission wavelength in the range of 600-660 nm in response to a third driving condition provided by the power supply.

[0125] The first, second, and third driving conditions may be the first, second, and third current densities, or the first, second, and third driving conditions may be the first, second, and third power densities.

[0126] The morphology of a quantum well (QW) in an active emission region can vary. For example, the emission region can contain a uniform QW with well-defined interfaces, or a fractured QW with less defined interfaces, breaks, or QW well width / component fluctuations, or a fractured QW with a similar localized center as a quantum dot. This control over the QW morphology determines the range of variable emission wavelengths that can be controlled and manipulated.

[0127] The luminescent region preferably contains a plurality of quantum wells (QWs). These quantum wells can be continuous. They can also be broken or discontinuous.

[0128] The variable wavelength LED may include a current constraining layer, or current limiting layer, which is a dielectric layer configured to constrain the current conducted through the lateral area of ​​the LED. Using a current constraining layer advantageously allows for further control of the current density in order to better control the peak emission wavelength of the LED.

[0129] In order to control the peak emission wavelength, the current confinement layer can advantageously enable manipulation of the power density provided to the variable wavelength LED.

[0130] The current-confining layer is preferably a dielectric material. For example, the current-confining layer can be any dielectric, such as SiO2, SiN, or SiNx.

[0131] The current-constraining layer can be located in various positions within the variable wavelength LED, as long as it constrains the current conducted through the lateral area of ​​the LED. The current-constraining layer can be positioned between the electrical n-contact and the electrical p-contact within the LED.

[0132] The current confinement layer can be located adjacent to either the n-doped or p-doped portion of the LED. For example, the current confinement layer can be located between the n-doped portion and the light-emitting region. Alternatively, the current confinement layer can be located between the light-emitting region and the p-doped portion. The current confinement layer can also be located between the electrical contact and the LED structure (n-doped portion, p-doped portion, and light-emitting region).

[0133] The current confinement layer preferably includes an aperture extending through it, or one or more apertures extending through it. The aperture is preferably located at the center of the current confinement layer. For example, the current confinement layer may include a circular opening at the center of the LED structure.

[0134] The variable wavelength LED can be configured such that the electrical contact contacts the LED structure through an aperture in the current confinement layer, and the area of ​​the aperture defines the contact area between the contact and the LED structure.

[0135] The lateral dimension of the aperture or individual apertures is preferably much smaller than the lateral dimension of the LED. By providing apertures through the dielectric current confinement layer, a high local current density can be achieved, which can advantageously enable improved control of the power passing through the LED.

[0136] For example, the lateral width (or diameter) of the aperture may be equal to or less than 50% of the lateral width of the LED structure (LED platform). The width of the aperture may be equal to or less than 45%, 40%, 35%, 30%, 25%, or 20% of the width of the LED structure.

[0137] The relative area of ​​the orifice to the total area of ​​the current confinement layer (blocking region) can be changed to modify the local current density.

[0138] The luminescent region preferably contains multiple quantum wells (QWs) or quantum dots, quantum wires, or other quantum nanostructures (MQWs).

[0139] In some specific embodiments, the light-emitting region comprises a plurality of quantum wells (QWs), and these quantum wells are sequential.

[0140] The inventors have discovered that non-uniformity in the luminescent region has a significant effect on broadening the range of emission wavelengths within which the luminescent region can emit light in response to variations in power supplied to the LED. In the prior art, non-uniformity in the luminescent region was generally considered a problematic defect that was unnecessary and should be avoided in any way possible, as the target was typically a high-quality, low-defect semiconductor wafer. The inventors have circumvented this bias in the art and have discovered that intentionally establishing non-uniformity in the luminescent region advantageously broadens the emission wavelength range and results in variable-wavelength LEDs emitting over a wider wavelength range than previously possible.

[0141] In alternative embodiments of the invention, the luminescent region is non-uniform, fractured, or discontinuous. This luminescent region can be intentionally introduced to achieve the effect of a carrier localization center in the InGaN quantum well, for example, various types of QW regions with different indium compositions and well widths and quantum barriers, resulting in non-uniformity, fractures, breaks, cracks, or discontinuities in the well width fluctuations of quantum wells, InGaN quantum dots or nanostructures, and quantum wells formed on polar, semi-polar, or non-polar facets.

[0142] In a preferred embodiment, the light-emitting region comprises a plurality of quantum wells (QWs), and these quantum wells are non-uniform, broken, or discontinuous.

[0143] These multiple quantum wells (QWs) may contain fluctuations in well width. For example, the well width of these QWs may fluctuate by at least 2%, 5%, 10%, 20%, 25%, or 50%, or 75%. These well width fluctuations may be variations between quantum wells (vertical) and within a single quantum well (lateral).

[0144] These plurality of QWs may contain fluctuations in the alloy composition. For example, the indium composition of these QWs may vary by at least 2%, 5%, 10%, 20%, 25%, 50%, or 75% in the luminescent region.

[0145] The inventors have discovered that fluctuations in the well width and / or alloy composition within the upper or lower interface of the QW can induce carrier localization centers. Any carrier localization center in the variable wavelength LED of this invention will induce a variable wavelength. The greater the density of carrier localization centers, the wider the achievable variable wavelength range.

[0146] The variable wavelength LED may include V-shaped pits that extend or propagate through the active light-emitting region. Preferably, the LED includes a plurality of V-shaped pits that extend through the light-emitting region.

[0147] Preferably, the variable wavelength LED may contain at least 1x10 7 V-groove density per square centimeter (measured from above when viewing the LED structure), for example, at least 5 x 1027 / square centimeter or at least 1x10 8 / square centimeters, for example, 1x10 7 / square centimeters to 5x10 9 V-shaped pit density per square centimeter.

[0148] The variable wavelength LED can contain less than 5x10 9 V-shaped pit density per square centimeter, for example, less than 1x10 9 / square centimeters or less than 5 x 10 8 V-shaped pit density per square centimeter.

[0149] V-pits are a known phenomenon in epitaxial semiconductor growth techniques, and the present art is known about methods for growing V-pits in semiconductor structures. For example, V-pits and their growth are described in the prior art in “The effect of nanometre-scale V-pits on electronic and optical properties and efficiency droop of GaN-based green light-emitting Diodes; Zhou et al.; Scientific Reports | (2018) 8:11053 | DOI:10.1038 / s41598-018-29440-4.

[0150] These V-shaped pits appear V-shaped when viewed in cross-section; however, in actual semiconductor structures grown from the bottom up using conventional epitaxial growth methods, they form conical or funnel-shaped voids. Although the pits have a V-shaped cross-section, they are typically hexagonal when viewed from above. The tips of these V-shaped pits always point downwards towards the earlier deposited semiconductor structure layer because the pits widen as subsequent epitaxial growth layers are deposited on top of the structure.

[0151] Although V-shaped pits are known in this art, they are generally considered problematic defects in semiconductor structures and are not desired, as the goal is usually high-quality, low-defect semiconductor wafers.

[0152] In the past, in unusual cases where semiconductor structures already contained V-pits, these V-pits were used as screening mechanisms to establish a higher bandgap region to prevent current carriers from falling below threading dislocations and becoming leakage paths.

[0153] However, in some preferred embodiments of the invention, the variable wavelength LED structure is intentionally made to contain V-shaped pits. These V-shaped pits extend downwards into the semiconductor structure far enough that they terminate in a layer below the active light-emitting region. This means that these V-shaped pits must extend through the thickness of the active light-emitting region.

[0154] The inventors have discovered that a V-shaped pit extending through the light-emitting area of ​​an LED structure can advantageously widen the range of emission wavelengths that a variable wavelength LED can emit within.

[0155] Because these V-shaped pits extend through the active region of the LED, during bottom-up epitaxial growth, planar quantum well (QW) layers are grown on the sloping sidewalls of these V-shaped pits. The QWs deposited on the pit sidewalls are twisted and stretched near the sides of these V-shaped pits, resulting in different thicknesses and compositions compared to the planar QWs on the surface of the structure.

[0156] Near these V-shaped pits, the QW layer of the semiconductor material is grown as a flat planar layer. Therefore, the active light-emitting region is planar near the V-shaped pits. However, at the location of the V-shaped pits, these active layers are twisted and stretched downwards along the sidewalls into the V-shaped pits. This stretching effect changes the thickness of the QW on the pit sidewalls, resulting in a different thickness compared to the planar QW layers formed on the rest of the LED structure.

[0157] The inventors have discovered that V-shaped pits can produce localized strain relaxation, and that the MQWs deposited on the sidewalls of these V-shaped pits have different thicknesses and compositions compared to the rest of the MQW, thus the MQWs in the regions of these V-shaped pits will produce different emission wavelengths.

[0158] The quantum wells grown on the sidewalls of these V-shaped pits are thinner than the bulk planar QWs elsewhere in the structure. This can affect the QW bandgap and allow the emission wavelength of the QW in this region to differ from that emitted by the planar QWs elsewhere in the structure. Furthermore, the QWs on the pit sidewalls may ultimately have a higher indium (In) content than the surrounding planar QWs because the sidewalls expose the semi-polar facets of the QWs, which contain more indium during epitaxial growth, resulting in more indium in the QWs in the V-shaped pit region than in the planar QWs near these pits. Higher indium content generally leads to a longer peak emission wavelength. Both QW thickness and indium content affect the emission wavelength produced by the emitting region. Therefore, the presence of V-shaped pits in an LED structure can advantageously modify the composition and thickness of the QW in the emitting region in a way that extends the range of emission wavelengths that can drive the LED to emit light within it.

[0159] V-shaped pits are typically grown from through dislocations in a semiconductor structure. When an additional layer is grown on top of a layer containing through dislocations, these dislocations extend upwards through the structure, and at a certain point, the dislocations widen to form a V-shaped pit. Typically, to produce "high-quality," low-defect wafers, those skilled in this art aim to maintain a low concentration of through dislocations.

[0160] Alternatively, V-shaped pits can be grown using a three-dimensional epitaxial growth mode. Three-dimensional epitaxial deposition technology is well-known in this art and is commonly used to grow "islands" or "cones" of semiconductor material on a template. By controlling the deposition of an LED structure using three-dimensional epitaxial deposition technology, V-shaped pits can be artificially grown in desired locations without the need to "seed" through dislocations to form them. Using this deposition control, the nadir of the pit can be established at desired locations within the structure, both in the desired lateral direction and at the desired height, such as in a specific layer beneath the active light-emitting region of the semiconductor structure.

[0161] The bottom of the V-shaped pit can be located in the interconnect layer of the semiconductor structure. This interconnect layer can be located between the porous region and the n-doped portion.

[0162] The bottom of the V-shaped pit can be located in the pre-strain layer of the semiconductor structure. This pre-strain layer can be located above the n-doped portion and below the light-emitting region.

[0163] Preferably, the variable wavelength LED includes a plurality of V-shaped pits extending through the active light-emitting region.

[0164] Preferably, the variable wavelength LED contains at least 1x10 7 / square centimeters, for example, at least 5x10 7 / square centimeter or at least 1x10 8 V-groove density per square centimeter (measured from above when viewing the LED structure). The LED may contain less than 5 x 10⁻⁶ pores per square centimeter. 9 V-shaped pit density per square centimeter, for example, less than 1x10 9 / square centimeters or less than 5 x 10 8 V-shaped pit density per square centimeter.

[0165] For example, the variable wavelength LED may contain 1x10 7 / square centimeters to 5x10 9 / square centimeter, or 5x10 7 / square centimeters to 5x10 9 / square centimeter, or 1x10 8 / square centimeters to 5x10 8 V-shaped pit density per square centimeter.

[0166] The variable wavelength LED may contain more than 0.1 V-shaped holes per square micrometer, or more than 1 V-shaped hole per square micrometer, or more than 2 V-shaped holes per square micrometer.

[0167] It is best to control the concentration of V-pits in variable wavelength LEDs, as too many V-pits can negatively affect LED luminescence by disrupting radiation overlap. For example, the LED may contain less than 10 V-pits per square micrometer, or less than 8 V-pits per square micrometer, or less than 6 V-pits per square micrometer.

[0168] In a preferred embodiment, the LED structure may contain no more than 10 LEDs per square centimeter. 9 One through-dislocation. Preferably, the semiconductor structure (typically a substrate, the porous region, and the interconnect layer) beneath the active light-emitting region contains no more than 10 through-dislocations per square centimeter. 9 One through-dislocation. The density of through-dislocations is best limited to this level so that further epitaxial growth will not generate too many V-shaped pits in the luminescent region.

[0169] The density and size (depth) of the V-shaped pits can be controlled. The size of the V-shaped pits can be controlled by the position of the pre-strained layer and the low-temperature nGaN layer at the beginning of these pits and by the growth conditions.

[0170] The morphology of a quantum well (QW) in an active emission region can vary. For example, the emission region can contain a uniform QW with well-defined interfaces, or a fractured QW with less defined interfaces, breaks, or QW well width / component fluctuations, or a fractured QW with a similar localized center as a quantum dot. This control over the QW morphology determines the range of variable emission wavelengths that can be controlled and manipulated.

[0171] The luminescent region preferably contains a plurality of quantum wells (QWs). These quantum wells can be continuous. They can also be broken or discontinuous.

[0172] If the quantum wave (QW) is continuous and its thickness and composition are uniform, the overlap of charge carriers can only occur in a well-defined and regular manner. On the other hand, if the QW is broken or discontinuous, many nanostructures will be generated, resulting in different band gaps and thus different colors of emission.

[0173] The light-emitting area and / or the LED may have a lateral dimension (width and length) greater than 100 micrometers and less than 300 micrometers. In this case, the LED may be referred to as a "mini-LED". In several preferred embodiments, the mini-LED may be square, circular, or a square with rounded corners and have dimensions such as 300 micrometers x 300 micrometers, 200 micrometers x 200 micrometers, or 100 micrometers x 100 micrometers.

[0174] Alternatively, the light-emitting area and / or the LED may have a lateral dimension (width and length) of less than 100 micrometers. In this case, the LED may be referred to as a "micro-LED". The micro-LED preferably has a lateral dimension of less than 80 micrometers, or 70 micrometers, or 60 micrometers, or 50 micrometers, or 30 micrometers, or 25 micrometers, or 20 micrometers, or 15 micrometers, or 10 micrometers, or 5 micrometers, or 3 micrometers, or 2 micrometers.

[0175] In several preferred embodiments, the micro-LED may be square, circular, or square with rounded corners and have dimensions such as 75 μm x 75 μm, 50 μm x 50 μm, 40 μm x 40 μm, 30 μm x 30 μm, 25 μm x 25 μm, 20 μm x 20 μm, or 10 μm x 10 μm, or 5 μm x 5 μm, or 2 μm x 2 μm, or 1 μm x 1 μm, or 500 nm x 500 nm or smaller.

[0176] Alternatively, the light-emitting area and / or the LED may have lateral dimensions (width and length) of less than 1 micrometer. In this case, the LED may be referred to as a "nano-LED". The nano-LED preferably has lateral dimensions of less than 500 nanometers, or 200 nanometers, or 100 nanometers, or 50 nanometers.

[0177] These LEDs can be circular, triangular, rectangular, square, elliptical, rhomboid, hexagonal, pentagonal, or any combination of these shapes. In cases where the pixel design is irregular, at least one dimension must fall within the dimensions defined above in order to classify the LED as a mini-LED or micro-LED. For example, the width or diameter of these LEDs is preferably less than 100 micrometers so that they are classified as micro-LEDs.

[0178] Porous region

[0179] These variable wavelength LEDs preferably contain one or more porous regions of a group III nitride material.

[0180] The n-type region, the light-emitting region, and the p-type region (which may be referred to as an LED structure or an LED diode structure) are preferably grown over a semiconductor template containing the porous region. The semiconductor template may also contain a number of semiconductor material layers configured to provide a suitable substrate for overgrowing the LED structure.

[0181] The porous region can be a porous layer, causing the light-emitting diode to contain a porous layer of group III nitride material. Preferably, the porous region can be a continuous porous layer, for example, formed from a continuous layer of porous group III nitride material.

[0182] The porous region may comprise a plurality of porous layers and, if desired, a plurality of non-porous layers. In several preferred embodiments of the invention, the porous region is an alternating stack of porous and non-porous layers, wherein the top surface of the stack defines the top of the porous region and the bottom surface of the stack defines the bottom of the porous region. The luminescent region may be formed over the stack of porous regions comprising porous layers of group III nitride material.

[0183] Each variable wavelength LED may contain its own porous region of group III nitride material, or alternatively, a shared porous region may be epitaxially connected to a plurality of such variable wavelength LEDs.

[0184] Manufacturing method

[0185] According to the second aspect, a method for manufacturing a display device can be provided. The display device is preferably a display device according to the first aspect described above.

[0186] The manufacturing method includes the following steps: forming a semiconductor structure on a substrate, the semiconductor structure including: a band-stop filter and a variable wavelength LED.

[0187] The variable wavelength LED may include:

[0188] n-doped portion;

[0189] p-doped portion; and

[0190] The light-emitting region located between the n-doped portion and the p-doped portion includes a light-emitting layer that emits light at a peak emission wavelength under an electrical bias voltage across it, wherein the variable wavelength LED is configured such that the peak emission wavelength of the LED is variable within an emission wavelength range of at least 40 nanometers.

[0191] The bandstop filter is configured to attenuate emitted light with wavelengths falling within the bandstop wavelength range, and the bandstop filter is configured such that the bandstop wavelength range is within the emission wavelength range of the variable wavelength LED.

[0192] The method may include the step of forming the variable wavelength LED above the substrate. The method may further include the step of forming the bandstop filter above the variable wavelength LED, and processing the semiconductor structure such that the bandstop filter is positioned between the variable wavelength LED and the light-emitting surface of the display device.

[0193] The method may include the following steps: forming the bandstop filter on the substrate and forming the variable wavelength LED above the bandstop filter.

[0194] The method may further include the following steps: removing the substrate from the first surface of the semiconductor structure and processing the semiconductor structure such that the first surface forms the light-emitting surface of the display device, wherein the bandstop filter is located between the variable wavelength LED and the light-emitting surface of the display device.

[0195] The method may include the following steps: overgrowing the variable wavelength LED over a porous region of a group III nitride material.

[0196] The method may include the following steps, if necessary: ​​porosify the n-doped regions of the group III nitride material to form porous regions of the group III nitride material.

[0197] The bandstop filter may contain one or more layers of porous group III nitride semiconductor material.

[0198] The method may include the following steps: forming the bandstop filter by alternating porous group III nitride semiconductor material with multiple porous layers and multiple non-porous group III nitride material; or forming the bandstop filter by alternating multiple layers of porous group III nitride material with a first porosity and multiple layers of porous group III nitride material with a second porosity. The thickness and refractive index of the layers in the bandstop filter may be configured to attenuate the wavelength in the bandstop using destructive interference.

[0199] The method may alternatively include the following steps: forming a comb-shaped bandstop filter by porousing a plurality of group III nitride semiconductor material layers, each having a different porosity.

[0200] The method may include the following steps: forming a porous region of a group III nitride material in at least one of the n-doped portion or the p-doped portion, and forming the luminescent region above the porous region of the group III nitride material.

[0201] The method may include the following steps: forming a light-emitting active region with a carrier local center in a quantum well, such as various types of QW regions with different indium compositions and well widths and quantum barriers, resulting in inhomogeneities, fractures, breaks, cracks, or discontinuous quantum wells, quantum dots or nanostructures, formed on polar, semi-polar or non-polar facets of the quantum well.

[0202] The luminescent region may contain a plurality of quantum wells (QWs), wherein such quantum wells are non-uniform, broken, or discontinuous. The plurality of QWs may contain indium composition fluctuations and / or well width fluctuations.

[0203] The method may include the following steps: forming one or more V-shaped pits in the LED structure, such that the V-shaped pits extend through the light-emitting area; preferably, forming a plurality of V-shaped pits extending through the light-emitting area. The method may also include the following steps: forming at least 0.1 V-shaped pits per square micrometer, or at least 1 V-shaped pit per square micrometer, or at least 2 V-shaped pits per square micrometer. The method may further include the following steps: forming a density of at least 1 x 10⁻⁶ V-shaped pits in the light-emitting area. 7 V-shaped pits per square centimeter, for example, at least 5x10 cm. 7 / square centimeter or at least 1x10 8 / square centimeter, for example, density 1x10 7 / square centimeters to 5x10 9 The method may include the following steps: forming a V-shaped pit with a density of less than 5 x 10⁻⁶ cm² in the luminescent area. 9 V-shaped pits per square centimeter, for example, with a density less than 1x10⁻⁶. 9 / square centimeters or less than 5 x 10 8 A V-shaped pit with a diameter of / square centimeters. Attached Figure Description

[0204] Referring now to the following accompanying drawings, several specific embodiments of the present invention will be described, wherein:

[0205] Figure 1 The illustration shows a display device that includes a color filter that converts white light into red, green, and blue emitted light.

[0206] Figure 2 The illustration shows a display device that includes a color converter that converts blue light into red and green emitted light.

[0207] Figure 3 The illustration shows a typical emission mode spectrum for a variable wavelength LED that emits in blue, green, and red emission modes.

[0208] Figure 4 The schematic diagram illustrates a display device according to a preferred embodiment of the present invention;

[0209] Figure 5 The schematic diagram illustrates a display device according to a preferred embodiment of the present invention;

[0210] Figure 6 The schematic diagram illustrates a display device according to a preferred embodiment of the present invention;

[0211] Figure 7a The schematic diagram illustrates the typical emission mode spectrum of a variable wavelength LED, which emits in blue, green, and red emission modes that overlap with the stopband of a band-stop filter.

[0212] Figure 7bThe comparison chart can be drawn by comparing sRGB monitors with and without band-stop filters. Figure 9a The color gamut emitted by a variable wavelength LED display device;

[0213] Figure 8a The schematic diagram illustrates a typical emission mode spectrum of a variable wavelength LED, which emits in blue, green, and red emission modes that overlap with the stopband of a first exemplary bandstop filter.

[0214] Figure 8b The comparison chart can be drawn by comparing sRGB monitors with and without band-stop filters. Figure 9a The color gamut emitted by a variable wavelength LED display device;

[0215] Figure 9a The schematic diagram illustrates the typical emission mode spectrum of a variable wavelength LED, which emits in blue, green, and red emission modes that overlap with the stopband of a second exemplary bandstop filter.

[0216] Figure 9b The comparison chart can be drawn by comparing sRGB monitors with and without band-stop filters. Figure 10a The color gamut emitted by a variable wavelength LED display device;

[0217] Figure 10a The schematic diagram illustrates the spectrum of a demonstrative emission mode of a variable wavelength LED, which emits in blue, green, and red emission modes that overlap with the two stopbands of an idealized bandstop filter;

[0218] Figure 10b The diagram shows that it can be seen from Figure 10a The emission spectrum emitted by the display device;

[0219] Figure 10c The comparison chart can be drawn by comparing sRGB monitors with and without dual-band stop filters. Figure 10a and 10b The color gamut emitted by a variable wavelength LED display device;

[0220] Figure 11a The schematic diagram illustrates the emission mode spectrum of a variable wavelength LED, which emits in blue, green, and red emission modes that overlap with the stopband of an idealized bandstop filter.

[0221] Figure 11b The comparison chart can be drawn by comparing sRGB monitors with and without band-stop filters. Figure 11b The color gamut displayed by a variable wavelength LED display device;

[0222] Figure 12a , 12b The experimentally measured transmission spectra of three commercially available filters with stop filters are shown in Figure 12c.

[0223] Figure 12d Illustration Figure 12a , 12b The transmission spectrum was experimentally measured using a combination of three band-stop filters of type 12c.

[0224] Figure 12e The illustration uses variable wavelength LEDs and Figure 12d The experimentally measured color gamut can be displayed using a band-stop filter;

[0225] Figure 13a The schematic diagram illustrates the emission mode spectrum of a variable wavelength LED emitting in blue, green, and red emission modes that overlap with two idealized stopbands of a first preferred stopband filter.

[0226] Figure 13b The diagram shows that it can be seen from Figure 13a The emission spectrum emitted by the display device;

[0227] Figure 13c The comparison chart can be drawn by comparing sRGB monitors with and without dual-band stop filters. Figure 13a and 13b The color gamut displayed by a variable wavelength LED display device;

[0228] Figure 14a The schematic diagram illustrates the emission mode spectrum of a variable wavelength LED that emits in blue, green, and red emission modes that overlap with the two idealized stopbands of a second preferred bandstop filter.

[0229] Figure 14b The diagram shows that it can be seen from Figure 14a The emission spectrum emitted by the display device;

[0230] Figure 14c The comparison chart can be drawn by comparing sRGB monitors with and without dual-band stop filters. Figure 14a and 14b The color gamut displayed by a variable wavelength LED display device;

[0231] Figure 15a The schematic diagram illustrates the emission mode spectrum of a variable wavelength LED that emits in blue, green, and red emission modes that overlap with two idealized stopbands of a third preferred bandstop filter.

[0232] Figure 15b The diagram shows that it can be seen from Figure 15a The emission spectrum emitted by the display device;

[0233] Figure 15c The comparison chart can be drawn by comparing sRGB monitors with and without dual-band stop filters. Figure 15a and 15bThe color gamut displayed by a variable wavelength LED display device;

[0234] Figure 16a The schematic diagram illustrates the emission mode spectrum of a variable wavelength LED that emits in blue, green, and red emission modes that overlap with two idealized stopbands of a fourth preferred bandstop filter.

[0235] Figure 16b The diagram shows that it can be seen from Figure 16a The emission spectrum emitted by the display device;

[0236] Figure 16c The comparison chart can be drawn by comparing sRGB monitors with and without dual-band stop filters. Figure 16a and 16b The color gamut displayed by a variable wavelength LED display device;

[0237] Figure 17a -c curve illustration Figures 13a to 16c The experimental measurements of WLD and transmission characteristics of four better bandstop filters were obtained.

[0238] Figure 18 The comparison chart can be drawn from an sRGB monitor and a monitor with nine variants of dual-band-stop filters. Figures 13a to 1 7. The color gamut emitted by the variable wavelength LED display device;

[0239] Figure 19a The schematic diagram illustrates a comparison of the original unfiltered emission spectrum with the emission mode spectra of a variable wavelength LED with three alternative bandstop filters, Notch_1, Notch_2, and Notch_3, emitting in blue, green, and red emission modes.

[0240] Figure 19b The curve diagram Figure 19a The brightness ratio of the blue, green and red emission modes in the four embodiments.

[0241] Figure 19c The comparison diagram can be drawn from Figure 19a and 19b The color gamut emitted by the four embodiments;

[0242] Figure 20a A schematic diagram illustrates a display device according to a preferred embodiment of the present invention; and

[0243] Figure 20b The schematic diagram illustrates a display device according to another preferred embodiment of the present invention. Detailed Implementation

[0244] To obtain multicolor light emission from a monochrome display, prior art has known that spectral elements, such as color filters and color converters, can be used.

[0245] For example, Figure 1 The schematic diagram illustrates a display device in which an array of white light emitters emits white light, and red, green, and blue color filters are positioned between the white light emitters and the light-emitting surface of the device. White light emitted from the white light emitters passes through these color filters, which convert the transmitted white light into red, green, and blue emitted light, respectively. In this configuration, each color filter requires its own dedicated white light emitter, which can be turned on and off to control the device to selectively emit red, green, and blue light. Therefore, these red, green, and blue color filters and their corresponding white light emitters can be controlled as spatially separated red, green, and blue pixels or sub-pixels.

[0246] Figure 2 The diagram illustrates an alternative scenario where a blue light emitter array emits blue light, and a red-to-green color converter is positioned between some of the blue light emitters and the emitting surface of the device. At least the blue light emitters are not covered by the color converters, allowing blue light emitted from the uncovered blue light emitters to be directly transmitted from the emitting surface of the display device.

[0247] Color converters are traditionally made of quantum dot or phosphor materials. Their function is to absorb blue light emitted by a light-emitter located below the color converter and re-emit the absorbed light at a new red or green wavelength.

[0248] In this configuration, each red converter must have its own dedicated blue light emitter, and each green converter must have its own dedicated blue light emitter. Each blue light emitter can be turned on and off, allowing the device to selectively emit red, green, and blue light. Therefore, the red and green converters and their corresponding blue light emitters can be controlled as spatially separated red and green pixels or sub-pixels, while the uncovered blue light emitters can be controlled as spatially separated blue pixels or sub-pixels.

[0249] These two solutions, color filtering and color conversion, can only be used in display devices that emit discrete primary color wavelengths using spatially separated sub-pixels.

[0250] Another known solution is to use a spectral filter, such as a bandpass filter with a passband centered on the primary color emission peak to narrow the FWHM of that emission peak.

[0251] As described above, in this invention, a variable wavelength LED is used to emit more than one peak emission wavelength. This means that the discrete colors emitted by the variable wavelength LED are not spatially separated, and therefore cannot be used... Figure 1 and2 Traditional color filters and color converters.

[0252] As described above, an optoelectronic display device containing variable wavelength LEDs can be operated to display any chromaticity within the displayable color gamut by controlling the LEDs to emit light in multiple emission modes. Each emission mode defines a primary color emission wavelength of the display device, and these primary color wavelengths are emitted in combination to provide a combined output signal with the desired output chromaticity and output luminous intensity.

[0253] The achievable color gamut size depends on the wavelength of the selected primary color emission mode, as well as the breadth of the emission spectrum emitted by the variable wavelength LED in each emission mode.

[0254] In this invention, the variable wavelength LED is preferably driven in a field-sequence mode. By enabling the variable wavelength LED to operate in multiple discrete emission modes, the same variable wavelength LED emits multiple primary color emission wavelengths.

[0255] The variable wavelength LED that can be used in this invention is called Dynamic Pixel Adjustment (DPT®) Variable Wavelength LED from ProTech Corporation, and is disclosed in International Patent Application No. PCT / GB2022 / 051997, which is published as World Patent No. WO2023 / 007174.

[0256] In several preferred embodiments, the same variable-wavelength pixel is used to emit all selected primary color emission wavelengths using field-sequential emission. In this case, all primary color emission wavelengths are selected within the emission wavelength range of the variable-wavelength LED.

[0257] As mentioned above, instead of driving a variable wavelength LED to emit a continuous emission wavelength by supplying a continuously changing drive current, this type of LED can be conveniently driven by selecting two, three, or more "primary color" emission wavelengths for the variable wavelength LED to operate. Then, similar to known field-sequence displays, an output signal with desired output chromaticity and output luminous intensity can be generated from the timing combination of light pulses of the primary color emission wavelengths.

[0258] For simplicity, the following embodiment refers to a preferred embodiment that uses three emission modes to drive a variable wavelength LED using a field-sequence driving method. In order to obtain a large color gamut triangle that can display output chromaticity, in this preferred embodiment, the LED is driven with first, second, and third emission modes to emit first, second, and third primary color emission wavelengths of red (R), green (G), and blue (B), respectively.

[0259] Figure 3The illustration shows typical emission modes of a variable wavelength LED in blue emission mode 402, green emission mode 404, and red emission mode 406. A drawback of using a variable wavelength LED instead of a single-wavelength LED is that, compared to a traditional single-wavelength LED, the variable wavelength LED has a broader emission peak spectrum (wider FWHM).

[0260] Taking the central green emission peak 404 as an example, the broad emission spectrum emitted by the variable wavelength LED includes wavelength overlap ranges 408 and 410 on both sides of the green peak emission wavelength. The green-blue overlap range 408 includes the wavelengths of light emitted in both green emission mode 404 and blue emission mode 402, while the green-red overlap range 410 includes the wavelengths of light emitted in both green emission mode 404 and red emission mode 406. The existence of these overlap ranges means that when the variable wavelength LED is driven to emit in green emission mode 404, this wavelength overlaps with the red and blue peaks, making the green mode spectrum appear less pure and "whiter" to the observer. Therefore, these broad emission spectra and overlap ranges mean that the purity of the emitted green light is lower, although the observed "average" wavelength may still be the same.

[0261] Because wavelengths within the green-blue overlap range 408 are emitted when the variable-wavelength LED is driven to operate in blue emission mode 402, the emitted spectrum includes a wide range of green wavelengths. This causes the observed wavelengths to shift towards green, although the perceived purity of the blue emission mode is affected less than in the green case described above.

[0262] The same applies to red emission. Since wavelengths within the green-red overlap range 410 are emitted when the variable-wavelength LED is driven to operate in red emission mode 406, the emitted spectrum includes a wide range of green wavelengths. This causes the observed wavelengths to shift away from red and towards green, although the perceived purity of the red emission mode is affected less than in the green case described above.

[0263] Table 1 illustrates the exemplary FWHM values ​​of the Dynamic Pixel Adjustment (DPT®) variable wavelength LED from ProTech, operating at three peak emission wavelengths.

[0264]

[0265] Table 1

[0266] As shown in Table 1, the typical emission spectrum of a variable wavelength LED with a wide emission range has a much wider FWHM than that of a conventional "monochrome" LED. This means that the emission peaks produced by a variable wavelength LED include a significant range overlapping with adjacent emission peaks, designed to produce different primary color emission colors. This reduces the purity of a single emission color, shifts the dominant wavelength away from the spectral peak wavelength, and reduces the size of the displayable color gamut.

[0267] Figure 4 A schematic diagram illustrates a display device 500 according to a preferred embodiment of the present invention. Figure 4 As shown, the display device 500 includes a substrate 510, a notch filter 520, and a variable wavelength LED 530. The notch filter is a high Q-factor bandstop filter, and the notch filter 520 and the variable wavelength LED 530 are epitaxially grown on the substrate 510 from a group III nitride material using a conventional method, for example, as mentioned in International Patent Application No. PCT / GB2022 / 051997, which is disclosed in World Patent No. WO2023 / 007174.

[0268] The exposed outer surface of the substrate 510 forms the light-emitting surface of the display device, such as Figure 4 As indicated by the arrow, the diagram shows the light emitted by the variable wavelength LED passing through the notch filter 520 and the substrate 510 before leaving the display device.

[0269] Since the notch filter is located between the variable wavelength LED and the light-emitting surface of the device, the light emitted by the LED is always filtered by the notch filter 520 before leaving the device.

[0270] Figure 5 and 6 The schematic diagram illustrates an alternative display device according to a specific embodiment of the present invention.

[0271] As illustrated Figure 5In the display device 600, a variable-wavelength LED 630, comprising a p-type region, an n-type region, and an active-emitting region containing multiple quantum wells (MQWs), is positioned on a substrate 610. A bandstop filter 620 is located above the variable-wavelength LED 630. The bandstop filter 620 is formed by a multilayer stack of porous and non-porous GaN, the layer thickness of which is selected to produce destructive interference that prevents the transmission of light with wavelengths within two bandstop wavelength ranges: one bandstop is located below the predetermined primary color emission wavelength of the LED, and the other bandstop is located above the predetermined primary color emission wavelength of the LED. When the variable-wavelength LED 630 is driven to emit its primary color emission wavelength, wavelengths close to the peak emission wavelength are transmitted through the bandstop filter 620 with near 100% intensity, while emission wavelengths further away from the peak emission wavelength are within the bandstop filter's bandstop and are therefore attenuated by destructive interference and prevented from escaping from the light-emitting surface of the device.

[0272] exist Figure 6 In the display device 700, three micro-LEDs 730, each a variable wavelength LED according to World Patent No. WO2023 / 007174, are connected to a bandstop filter 720. Although these LEDs and the bandstop filter are grown on a substrate, the substrate has been removed from the display device 700. Figure 5 In this design, the bandstop filter 720 is formed by a multilayer stack of porous and non-porous GaN, the layer thickness of which is selected to produce destructive interference that prevents light transmission within the two bandstop wavelength ranges. As further described below, these two bandstops are spectrally positioned between the three predetermined primary color emission wavelengths of the LED, such that the bandstop filter 720 attenuates emitted wavelengths falling within the overlapping range shared by more than one primary color emission peak.

[0273] Figure 7a The schematic diagram illustrates the typical emission mode spectrum of a variable wavelength LED, which emits in blue emission mode 802, green emission mode 804, and red emission mode 806. These emission modes overlap with the transmission spectrum of a bandstop filter characterized by an idealized bandstop 820.

[0274] As explained Figure 3 As described above, the green-blue overlap range 808 includes the wavelengths of light emitted in both the green emission mode 804 and the blue emission mode 802, while the green-red overlap range 810 includes the wavelengths of light emitted in both the green emission mode 804 and the red emission mode 806.

[0275] The stopband 820 of this bandstop filter is positioned to attenuate wavelengths ranging from approximately 570 nm to 620 nm, covering most of the green-red overlap range 810. In an idealized stopband 820, emitted wavelengths falling within this stopband wavelength range are attenuated by approximately 80% to 20% of their original intensity.

[0276] In practice, this means that when a variable-wavelength LED is driven to emit at its green primary color emission peak 804, a portion of the LED's inherent green peak width, specifically the wavelength of 570-620 nanometers, is filtered and its intensity reduced by the stopband 820. This effectively narrows the width of the emission peak emitted by the LED in green emission mode, resulting in a purer "green" emission. Similarly, when a variable-wavelength LED is driven to emit at its red primary color emission peak 806, a portion of the LED's inherent red peak width, specifically the wavelength of 570-620 nanometers, is filtered and its intensity reduced by the stopband 820. This effectively narrows the width of the emission peak emitted by the LED in red emission mode, resulting in a purer "red" emission.

[0277] like Figure 7b As shown, using a bandstop filter to narrow the emission peak increases the size of the displayable color gamut by 16.6%, because the narrower emission peak and purer emission color shift the position of the filtered primary color emission wavelength in the CIE xy color space.

[0278] Figure 7b The diagram illustrates the relative color gamut that a traditional sRGB display can show, formed by three discrete red, green, and blue sub-pixels using three primary colors, and compares it with... Figure 3 and 7a A comparison of variable wavelength LEDs driven in field-sequence mode with the three primary color emission wavelengths 802, 804, and 806, and with the addition of Figure 7a Comparison of the same variable wavelength LEDs with stop filters. Of the three color gamuts that can be displayed using these three options, the one with the largest area increase of 16.6% is... Figure 7a The display has a built-in stop filter.

[0279] The function of this bandstop filter is to reduce the spectral power on one side of the selected "primary color" peak emission wavelength. For example, the bandstop filter may have a stopband selected to reduce the spectral power on the green side of the blue emission peak or on the blue side of the green emission peak. Unlike prior art bandpass filters, the stopband of this bandstop filter targets the spectral region between the primary color emission peaks, rather than the primary color emission peaks themselves. The advantage of this configuration compared to others is that it is effective regardless of the color (emission mode) emitted by the variable wavelength LED: a bandstop filter with a stopband in blue or green will not affect red emission, and a bandstop filter with a stopband in green or red will not affect blue emission.

[0280] similar Figure 7a , Figure 8a The illustration shows the peak values ​​of three typical primary color emission modes of a variable wavelength LED, which emits in blue, green, and red emission modes that overlap with the stopband 920 of the first exemplary bandstop filter.

[0281] As mentioned above, the bandstop filter can be formed from a periodic porous / non-porous GaN structure, and various bandstop filters can be used in this invention.

[0282] Illustration Figure 8a The exemplary bandstop filter consists of 15 alternating periods of the following two elements: a 54.9 nm thick non-porous GaN layer (refractive index n=2.45) and a 76.25 nm thick porous GaN layer (n=2.15).

[0283] like Figure 8b As shown, compared to the same variable wavelength LED without a stopband filter, the peak narrowing effect of the stopband increases the color gamut area that the display device can display by 22.2%.

[0284] similar Figure 7a and 8a , Figure 9a The illustration shows the peak values ​​of three typical primary color emission modes of a variable wavelength LED, which emits blue, green, and red emission modes that overlap with the stopband 1020 of the second exemplary bandstop filter. Unlike... Figure 8a Modeled bandstop filter Figure 9a The stopband 1020 is located in the blue-green overlap range where the emission peaks of the blue and green primary colors overlap.

[0285] Illustration Figure 9a The exemplary bandstop filter consists of 15 alternating periods of the following two elements: a 45 nm thick non-porous GaN layer (refractive index n = 2.45) and a 62.5 nm thick porous GaN layer (n = 2.15).

[0286] like Figure 9b As shown, compared to the same variable wavelength LED without a stopband filter, the peak narrowing effect of the stopband increases the color gamut area that the display device can display by 0.2%.

[0287] Figure 10a The illustration shows an exemplary emission mode spectrum of a variable wavelength LED emitting in blue, green, and red emission modes that overlap with the two stopbands of an idealized bandstop filter. These two stopbands are provided by two bandstop filters, each configured to provide its own stopband. The two bandstop filters are stacked one on top of the other in the path of the emitted light, such that the light must pass through both filters before leaving the device. This effectively forms a dual-stimulated bandstop filter.

[0288] Table 2 shows the peak wavelength and FWHM value of the Dynamic Pixel Adjustment (DPT®) variable wavelength LED from ProTech, which operates with three peak emission wavelengths.

[0289]

[0290] Table 2

[0291] The three emission peaks are illustrated in the diagram. Figure 10a Furthermore, it overlaps with the idealized transmission characteristics of bandstop filters with blue-green stopband 1120 and green-red stopband 1125. In these idealized stopbands, the emitted wavelength is attenuated to zero, while 100% transmission occurs outside the stopband.

[0292] Figure 10b The diagram illustrates how the wavelength attenuated by the two stopbands 1120 and 1125 can be obtained from... Figure 10a The final emission spectrum emitted by the display device. Three narrowed emission peaks remain in the spectrum. Both the blue emission peak 1102 and the red emission peak 1106 are narrowed, and the emission wavelength of the red peak is slightly shifted. The green emission peak 1104 is significantly narrowed because most of the original green emission peak is covered by the green-red stopband 1125, and the remaining green peak is shifted to a shorter wavelength.

[0293] Figure 10c The comparison can be made between sRGB displays and those with and without dual-stimulation bandstop filters. Figure 10a and 10b The color gamut emitted by a variable wavelength LED display device. For example... Figure 10c As shown, the color gamut of an unfiltered display is relatively small because the emission peaks of the three primary colors are close together. However, the two stopbands serve to shift the effective primary color peak wavelengths and narrow the emission peaks, thereby significantly expanding the color gamut that can be displayed using a filtered display.

[0294] Figure 11a Diagram and Figure 10a A similar specific embodiment is shown, but it has only one band-stop filter stopband 1125, which attenuates wavelengths in the range of 540 nm to 610 nm.

[0295] Figure 11b The comparison can be made between sRGB displays and those with and without band-stop filters. Figure 11b The color gamut displayed by a variable wavelength LED display device. Because the stopband 1125 attenuates only a very small portion of the wavelength emitted when the variable wavelength LED is driven in blue emission mode, the blue primary corner in the CIE xy color gamut is almost indistinguishable between the filtered and unfiltered color gamuts. However, because the stopband 1125 attenuates a large portion of the wavelength emitted in green and red emission modes, the green and red primary corners in the CIE xy color gamut of an unfiltered display are significantly different from those of a filtered display, and this variation expands the color gamut that can be displayed by driving variable wavelength LEDs using these three primary color emission modes. Figures 12a to 12c The diagram shows the transmission spectra obtained by measuring three readily available bandstop filters. Figure 12d The illustration shows an experiment measuring the transmission spectrum of a combination of three identical filters stacked one on top of another, such that the emitted light passes through all three filters before the transmission is measured. (Illustrated in...) Figure 12a , 12b The filters of type 12a are commercially available notch filters with stopbands having center wavelengths of 514 nm, 561 nm and 594 nm.

[0296] Figure 12e The illustration uses variable wavelength LEDs and Figure 12d The combined bandstop filter can display the experimentally determined color gamut. Figure 12e The illustration shows how adding a filter expands the displayable area of ​​the color gamut compared to the unfiltered (NF) gamut. These experimental results were obtained using off-the-shelf bandstop filters, and the filtering was not ideal. However, the comparison between "with filter" and "NF" (without filter) shows that the invention works as expected.

[0297] Figure 13a-18 The illustration shows identical variable-wavelength LEDs with different band-stop filters, all driven by the same three primary red, green, and blue emission wavelengths. In each case, the unfiltered spectrum consists of a red primary peak at 630 nm, a green primary peak at 540 nm, and a blue primary peak at 440 nm, all with an FWHM of 50 nm.

[0298] Although the peak emission wavelengths are the same in all cases, the use of bandstop filters with different stop wavelength ranges, different center wavelengths, and different widths means that the manifest transmission wavelengths (WLDs) of the three primary color peaks differ between specific embodiments. The transmission and purity of the transmitted light also vary depending on the characteristics of the bandstop filter.

[0299] similar Figure 10a , 10b and 10c, Figure 13a , 13b The diagram 13c illustrates the simulated effect of an idealized dual-band-stop filter on the RGB primary color emission spectrum and the idealized display color gamut of a variable wavelength LED. Figure 13a The illustration shows the emission mode spectrum of a variable wavelength LED that emits in blue, green, and red emission modes that overlap with the two idealized stopbands of a first preferred bandstop filter. Figure 13b The image shows the spectrum transmitted from the device after filtering.

[0300] In the first preferred bandstop filter, the first bandstop is centered at a wavelength of 478 nm and has a bandstop width of 75 nm, while the second bandstop is centered at a wavelength of 585 nm and has a bandstop width of 90 nm.

[0301] As described above, the two stopbands can be established by forming the bandstop filter from two stacked bandstop filter portions, each configured to generate its own stopband. This filter can be integrated into a variable wavelength LED device using a porous (Al,In)GaN layer, or formed from conventional dielectric materials such as SiO2 / TiO2.

[0302] This first preferred bandstop filter advantageously allows filtering of the emission spectrum to produce red, green, and blue light of extremely high purity in the transmission spectrum.

[0303] For the first preferred bandstop filter, Table 3 lists the percentage of transmitted light, the dominant wavelength (WLD), and the purity of transmitted light for each primary color emission peak.

[0304]

[0305] Table 3

[0306] Figure 13c The comparison diagram can be illustrated by comparing sRGB displays with and without dual-band stop filters. Figure 13a and 13b The analog color gamut displayed by a variable wavelength LED display device. This figure shows how adding dual bandstop filters to a variable wavelength LED significantly expands the area of ​​the triangle defining the displayable color gamut.

[0307] This first superior bandstop filter effectively narrows the emission of each primary color, improving purity and expanding the color gamut.

[0308] similar Figures 13a to 13c , Figure 14a , 14b The idealized second-best dual-band-stop filter, illustrated in Figure 14c, demonstrates the simulated effect on the RGB primary color emission spectrum and the idealized display color gamut of a variable wavelength LED. Figure 14a The illustration shows the emission mode spectrum of a variable wavelength LED that emits in blue, green, and red emission modes that overlap with the two stopbands of a second preferred bandstop filter. Figure 14b The image shows the spectrum transmitted from the device after filtering.

[0309] The second preferred bandstop filter has a first bandstop centered at a wavelength of 490 nm and a bandstop width of 30 nm, while the second bandstop is centered at a wavelength of 585 nm and has a bandstop width of 24 nm.

[0310] This second, preferred bandstop filter advantageously allows filtering of the emission spectrum to produce highly efficient (high-transmission) red, green, and blue light in the transmission spectrum.

[0311] For the second preferred bandstop filter, Table 4 lists the percentage of transmitted light, the dominant wavelength (WLD), and the purity of transmitted light for each primary color emission peak.

[0312]

[0313] Table 4

[0314] Figure 14c The comparison chart can be drawn by comparing sRGB monitors with and without dual-band stop filters. Figure 14a and 14b The analog color gamut displayed by a variable wavelength LED display device. This figure shows how adding a dual-band-stop filter to a variable wavelength LED only slightly expands the area of ​​the triangle defining the displayable color gamut.

[0315] Figure 15a -c illustrates a simulation of a variable wavelength LED emitting in blue, green, and red emission modes, with an idealized third-best-fit filter having two stopbands.

[0316] The third preferred bandstop filter has a first stopband centered at a wavelength of 500 nm with a stopband width of 40 nm, and a second stopband centered at a wavelength of 582.5 nm with a stopband width of 65 nm. This third preferred bandstop filter advantageously allows filtering of the emission spectrum to produce red, green, and blue light of extremely high purity in the transmission spectrum, resulting in… Figure 15c This filter significantly expands the displayable color gamut.

[0317] For the third preferred bandstop filter, Table 5 lists the percentage of transmitted light, the dominant wavelength (WLD), and the purity of transmitted light for each primary color emission peak.

[0318]

[0319] Table 5

[0320] Figure 16a -c illustrates a simulation of a variable wavelength LED emitting in blue, green, and red emission modes, with an idealized fourth-best-fit filter having two stopbands.

[0321] The fourth preferred bandstop filter has a first bandstop centered at a wavelength of 495 nm and a bandstop width of 30 nm, while a second bandstop centered at a wavelength of 587.5 nm and a bandstop width of 55 nm.

[0322] This fourth preferred bandstop filter advantageously allows filtering of the emission spectrum to produce highly efficient (high-transmission) red, green, and blue light in the transmission spectrum. Figure 16c The results show that, without a band-stop filter, the filter significantly expands the displayable color gamut relative to the same primary color; however, the purity of the transmitted green primary color peak is slightly reduced, meaning that the displayable color gamut is slightly smaller than that of the third better band-stop filter.

[0323] For the fourth preferred bandstop filter, Table 6 lists the percentage of transmitted light, the dominant wavelength (WLD), and the purity of transmitted light for each primary color emission peak.

[0324]

[0325] Table 6

[0326] Figure 17a The curve of -c depicts the first to fourth bandstop filters better. The transmission measurement values ​​are listed in Tables 3 to 6 above.

[0327] like Figure 17a As shown in -c, by changing the center wavelength and width of the stopband, it is possible to control the transmission of the red, green, and blue primary color emission peaks over a wide range, with some filter designs providing extremely high transmission at wavelengths outside the stopband.

[0328] By changing the layer thickness, arrangement, and refractive index of the material in the bandstop filter, the center wavelength and bandstop width of the bandstop filter can be controlled.

[0329] Figure 18 The comparison chart can be drawn from an sRGB monitor and a monitor with nine variants of dual-band-stop filters. Figures 13a to 1 7. Color gamut emitted by the variable wavelength LED display device.

[0330] Table 7 lists the details of the nine bandstop combinations tested, showing the dominant transmission wavelengths of all three primary color peaks after the emitted light is filtered through a dual-bandstop filter. In all cases in Table 7, the lower wavelength bandstop is 75 nm wide, and the higher wavelength bandstop is 90 nm wide. Filter tolerances are assumed to be ±5 nm of the center wavelength.

[0331]

[0332] Table 7

[0333] The figures in Table 7 are calculation results, and the graphs illustrate the impact of manufacturing variability on filter performance. The reference design (bold) is the first preferred bandstop filter in Figure 13, and Table 7 includes eight variations that allow for changes in the center wavelength of the two bandstops to -5 nm, 0 nm, or +5 nm. For example, for filters made with dielectrics (e.g., SiO2, TiO2), tolerances at the center of the bandstops can be easily controlled. These simulations demonstrate that the filter design is not very sensitive to manufacturing variability that can affect the center wavelength of the bandstops.

[0334] Figure 19a , 19b The diagram in Figure 19c shows four simulations of a variable wavelength LED emitting in blue, green, and red emission modes. The emission spectra of the original unfiltered variable wavelength LED are compared with those of the same LED filtered by three different bandstop filters (notch filters) with different stopband widths.

[0335] Table 8 below lists the stopband widths of these three bandstop filters (Notch_1, Notch_2, and Notch_3) and the center wavelength of the emission peaks after R, G, and B filtering.

[0336]

[0337] Table 8

[0338] Figure 19b The brightness ratios of the blue, green, and red emission modes for the original, Notch_1, Notch_2, and Notch_3 specific embodiments are depicted. As the bandstop width increases, the proportion of emitted light blocked by the bandstop filter increases, thus reducing the brightness of the emission modes.

[0339] Different bandstop widths and positions also affect the color gamut that each of the Notch_1, Notch_2, and Notch_3 embodiments can display relative to the original (unfiltered) variable wavelength LED. Although the presence of bandstop filters in these embodiments reduces the emitted brightness relative to the unfiltered LED, these bandstop filters block the overlapping wavelengths of the R, G, and B emission peaks. This narrows the emission peaks and increases the purity of the emitted R, G, and B light, thus expanding the color gamut that the device can display relative to the original unfiltered LED.

[0340] Figure 19C illustrates the relative sizes of the color gamut in the CIE xy color space displayed by a raw, unfiltered variable-wavelength LED and by the same LED filtered with Notch_1, Notch_2, and Notch_3 bandstop filters. Table 9 lists the CIE xy measurements, luminance ratios, and color coverage ratios relative to the National Television Standards Committee (NTSC) color gamut standard.

[0341]

[0342] Table 9

[0343] All specific embodiments with stopband filtering demonstrate a larger color gamut (higher color coverage) than unfiltered variable wavelength LEDs, but a lower luminance ratio. The Notch_3 stopband filter with the widest stopband achieves the highest color coverage but the lowest luminance ratio, while the Notch_1 filter achieves a smaller color coverage but the highest filtered sample luminance ratio.

[0344] Since the requirements for brightness and color gamut vary significantly in different situations, the bandstop filter best suited for each application can be selected. However, in some cases, the Notch_2 bandstop filter offers a favorable balance between high color coverage (large displayable color gamut) and a suitable high brightness ratio for R, G, and B emission modes.

[0345] Figure 20a The schematic diagram illustrates a display device according to a specific embodiment, wherein a variable wavelength LED microdisplay 2030 and a notch filter 2020 are located on the same wafer, wherein the notch filter 2020 is positioned between the LEDs of the microdisplay 2030 and the sequence of microlenses 2010. In this specific embodiment, the notch filter 2020 may be integrated into the device and formed from a porous (Al,In) GaN layer grown on the LED wafer using conventional deposition techniques, or the filter may be formed from a conventional dielectric material (e.g., SiO2 / TiO2) and deposited on the LED wafer prior to attaching the microlenses.

[0346] Figure 20b The schematic diagram illustrates a display device according to an alternative embodiment, wherein a sequence of microlenses 2110 is positioned above a variable wavelength LED microdisplay 2130, and a notch filter 2120 is positioned between the microlenses and a projector lens 2140.

[0347] In both of these embodiments, the notch filter is positioned to filter the light emitted by the variable-wavelength LEDs of the microdisplay before it leaves the device to be observed. These two embodiments offer their own advantages in different applications.

Claims

1. A display device comprising: Variable wavelength light-emitting diodes (LEDs); and A stop filter is located between the variable wavelength LED and the light-emitting surface of the display device; The variable wavelength LED comprises an n-doped portion, a p-doped portion, and a light-emitting region located between the n-doped portion and the p-doped portion, the light-emitting region being configured to emit light at a peak emission wavelength under a bias voltage across it. The variable wavelength LEDs are configured such that the peak emission wavelength of the variable wavelength LEDs can be varied within an emission wavelength range of at least 40 nanometers by changing the driving conditions provided to the variable wavelength LEDs; The bandstop filters are configured to attenuate emitted light whose wavelengths fall within the bandstop wavelength range; and The bandstop filters are configured such that the bandstop wavelength range is within the emission wavelength range of the variable wavelength LED.

2. The display device of claim 1, wherein the variable wavelength LED is a dynamically color-tunable LED, wherein the peak emission wavelength of the LED is adjusted by changing the driving conditions provided to the LED.

3. The display device according to claim 1 or 2, wherein the light-emitting diode comprises a porous region of a group III nitride material.

4. The display device of claim 3, wherein one of the n-doped portion or the p-doped portion comprises the porous region of a group III nitride material.

5. The display device of claim 3, wherein the n-doped portion, the p-doped portion, and the light-emitting region are provided on a substrate comprising a group III nitride material in the porous region.

6. The display device according to any one of claims 1 to 5, wherein the emission wavelength of the variable wavelength LED is continuously variable within an emission wavelength range in response to driving conditions provided by the power supply that are continuously varied within a driving range.

7. The display device according to any one of claims 1 to 6, wherein the peak emission wavelength can be controlled within an emission wavelength range of at least 50 nm, or at least 60 nm, or at least 70 nm, or at least 80 nm by changing the driving conditions provided to the variable wavelength LED, preferably within a range of 100 nm, or 110 nm, or 120 nm, or 140 nm, or 160 nm, or 180 nm, or 200 nm, or 400 nm, or 450 nm.

8. The display device according to any one of claims 1 to 7, wherein the bandstop wavelength range is narrower than the emission wavelength range of the variable wavelength LED, such that the emitted wavelength in a portion of the emission wavelength range is not attenuated by the bandstop filter.

9. The display device of claim 8, wherein the bandstop filter is configured such that the bandstop wavelength range attenuates a portion of the emission wavelength range of the variable wavelength LED, but transmits shorter emission wavelengths below the bandstop wavelength range and longer emission wavelengths above the bandstop wavelength range.

10. The display device according to any one of claims 1 to 9, wherein the display device is configured to operate the variable wavelength LED in a plurality of discrete emission modes by providing a plurality of discrete driving conditions to the variable wavelength LED, wherein the variable wavelength LED emits different peak emission wavelengths in each discrete emission mode, and wherein each emission mode produces an emission mode spectrum containing wavelengths around the peak emission wavelength.

11. The display device of claim 10, wherein the bandstop filter is configured to attenuate the wavelength of emitted light emitted in a plurality of emission mode spectra within an overlapping range.

12. The display device of claim 10 or 11, wherein the bandstop filter is configured such that the bandstop does not contain any peak emission wavelengths generated by the discrete emission modes.

13. The display device of claim 10, 11 or 12, wherein the bandstop filter is configured such that the bandstop position is between the peak emission wavelengths of the discrete emission modes, such that the bandstop filter attenuates the wavelengths between the peak emission wavelengths.

14. The display device of claim 11, wherein one or more of the peak emission wavelengths generated by the discrete emission modes fall within the stopband, but wherein a portion of the emission mode spectrum generated by the emission mode is not within the stopband.

15. The display device according to any one of claims 1 to 14, wherein the variable wavelength LED can be controlled in a first mode to emit a first peak emission wavelength in the emission wavelength range in response to a first driving condition provided by the power supply, and can be controlled in a second mode to emit a second peak emission wavelength in the emission wavelength range in response to a second driving condition provided by the power supply, wherein the stopband wavelength range is located between the first peak emission wavelength and the second peak emission wavelength to attenuate overlapping emission wavelengths emitted in both the first mode and the second mode.

16. The display device of claim 15, wherein the bandstop filter is configured to attenuate the emitted wavelength in the spectral overlap range in both the first mode and the second mode.

17. The display device of claim 16, wherein the first peak emission wavelength is less than 570 nm and the second peak emission wavelength is greater than 610 nm, causing the variable wavelength LED to emit green light in response to the first driving condition and red light in response to the second driving condition, and wherein the stop band of the band-stop filter is configured to attenuate the wavelength between the first peak emission wavelength and the second peak emission wavelength.

18. The display device according to any one of claims 1 to 17, wherein the bandstop filter is configured to attenuate wavelengths in a plurality of bandstop wavelength ranges within the emission wavelength range of the variable wavelength LED, and the bandstop filter is configured to have a plurality of bandstops within the emission wavelength range of the variable wavelength LED.

19. The display device according to any one of claims 1 to 17, comprising: a plurality of discrete bandstop filters with wavelengths ranging within the emission wavelength range of the variable wavelength LED, the plurality of bandstop filters being configured to attenuate the scattering wavelengths within the emission wavelength range of the variable wavelength LED.

20. The display device of claim 19, wherein a plurality of band-stop filters are located between the variable wavelength LED and the light-emitting surface of the display device, such that light emitted from the variable wavelength LED must pass through the plurality of band-stop filters before exiting the display device.

21. The display device according to any one of claims 1 to 20, wherein the variable wavelength LED can be controlled by changing the driving conditions provided to the variable wavelength LED between three discrete emission modes to emit three discrete peak emission wavelengths.

22. The display device according to any one of claims 1 to 21, wherein the variable wavelength LED can be controlled in a first mode to emit at a first peak emission wavelength in response to a first driving condition provided by the power supply; can be controlled in a second mode to emit at a second peak emission wavelength in response to a second driving condition provided by the power supply; and can be controlled in a third mode to emit at a third peak emission wavelength in response to a third driving condition provided by the power supply.

23. The display device of claim 22, wherein the bandstop filter is configured such that the bandstop attenuates overlapping wavelengths emitted in the first mode and the second mode, and wherein the display device includes a bandstop filter with a second bandstop configured to attenuate overlapping wavelengths emitted in the second mode and the third mode.

24. The display device according to any one of claims 1 to 23, wherein the variable wavelength LED is controllable to emit a blue peak emission wavelength in response to a first driving condition provided by the power supply; controllable to emit a green peak emission wavelength in response to a second driving condition provided by the power supply; and controllable to emit a red peak emission wavelength in response to a third driving condition provided by the power supply.

25. The display device according to any one of claims 1 to 24, wherein the variable wavelength LED is controllable to emit a first peak emission wavelength in the range of 400-500 nanometers in response to a first driving condition provided by the power supply; It can be controlled to emit a second peak emission wavelength in the range of 500-560 nanometers in response to a second driving condition provided by the power supply; It can also be controlled to emit a third peak emission wavelength greater than 600 nanometers in response to a third driving condition provided by the power source.

26. The display device according to any one of claims 1 to 25, wherein the variable wavelength LED is controllable to emit a first peak emission wavelength in the range of 430-470 nanometers in response to a first driving condition provided by the power supply; It can be controlled to emit a second peak emission wavelength in the range of 510-560 nanometers in response to a second driving condition provided by the power supply; It can also be controlled to emit a third peak emission wavelength in the range of 600-660 nanometers in response to a third driving condition provided by the power supply.

27. The display device of claim 25 or 26, wherein the bandstop filter is configured to attenuate the emitted wavelength in a first stopband located between the first peak emission wavelength and the second peak emission wavelength, and to attenuate the emitted wavelength in a second stopband located between the second peak emission wavelength and the third peak emission wavelength.

28. The display device according to any one of claims 22 to 27, wherein the first driving condition, the second driving condition and the third driving condition are first, second and third driving currents having different values ​​corresponding to the first, second and third current densities.

29. The display device according to any one of claims 1 to 28, wherein the bandstop filter is an optical notch filter.

30. The display device according to any one of claims 1 to 29, wherein the bandstop filter is a dual-stimulated bandstop filter or a dual-stop bandstop filter configured to attenuate the emitted wavelength in the two separated stop bands.

31. The display device of claim 30, wherein the bandstop filter is configured to attenuate the transmitted wavelength in a first stopband located between the blue peak wavelength and the green peak wavelength, and to attenuate the transmitted wavelength in a second stopband located between the green peak wavelength and the red peak wavelength.

32. The display device according to any one of claims 1 to 31, wherein the bandstop filter has a bandstop with a width of at least 10 nanometers, or 20 nanometers, or 25 nanometers, or 30 nanometers.

33. The display device according to any one of claims 1 to 32, wherein the bandstop filter has a bandstop with a width of less than 75 nanometers, or 60 nanometers, or 50 nanometers.

34. The display device according to any one of claims 1 to 33, wherein the bandstop filter comprises one or more layers of porous group III nitride semiconductor material.

35. The display device of claim 34, wherein the bandstop filter comprises a layered structure, wherein a first complex layer having a first refractive index alternates with a second complex layer having a second refractive index.

36. The display device of claim 34 or 35, wherein the bandstop filter comprises a layered structure, wherein multiple layers of porous group III nitride semiconductor material alternate with multiple layers of non-porous group III nitride material, or wherein multiple layers of porous group III nitride material with a first porosity alternate with multiple layers of porous group III nitride material with a second porosity.

37. The display device according to claim 35 or 36, wherein the thicknesses of the layers in the bandstop filter are configured to attenuate the wavelength in the bandstop by destructive interference.

38. The display device according to any one of claims 1 to 34, wherein the bandstop filter comprises a comb filter.

39. The display device of claim 38, wherein the comb filter comprises one or more porous layers of a group III nitride semiconductor material, wherein the porosity of the porous layer varies with the layer thickness, causing the refractive index of the porous layer to vary with the layer thickness.

40. The display device according to any one of claims 1 to 39, comprising a plurality of variable wavelength LEDs, each configured to receive its own power supply, wherein each of the plurality of variable wavelength LEDs is controllable such that the peak emission wavelength of each LED can be controlled by changing the driving conditions provided to the LED, wherein the display device is configured such that light emitted from each LED passes through a band-stop filter before exiting the display device.

41. The display device of claim 40, wherein the display device is configured such that light emitted by the plurality of variable wavelength LEDs passes through the same band-stop filter before exiting from the light-emitting surface of the display device.

42. A method of manufacturing a display device according to claim 1, comprising the steps of: forming a semiconductor structure on a substrate, the semiconductor structure comprising a band-stop filter and a variable wavelength LED, the variable wavelength LED comprising: n-doped portion; p-doped portion; and The light-emitting region is located between the n-doped portion and the p-doped portion, the light-emitting region comprising a light-emitting layer that emits light at a peak emission wavelength under an electrical bias voltage across it, wherein the variable wavelength LEDs are configured such that the peak emission wavelength of the variable wavelength LEDs is variable within an emission wavelength range of at least 40 nanometers. The bandstop filters are configured to attenuate emitted light whose wavelengths fall within the bandstop wavelength range; and The bandstop filters are configured such that the bandstop wavelength range is within the emission wavelength range of the variable wavelength LED.

43. The method of claim 42, further comprising the step of: forming the variable wavelength LED over the substrate.

44. The method of claim 42 or 43, further comprising the steps of: forming the bandstop filter over the variable wavelength LED, and processing the semiconductor structure such that the light-emitting surface of the display device is located over the bandstop filter.

45. The method of claim 42, further comprising the steps of: forming the bandstop filter on the substrate and forming the variable wavelength LED above the bandstop filter.

46. ​​The method of claim 45, further comprising the steps of: removing the substrate from a first surface of the semiconductor structure, and processing the semiconductor structure such that the first surface forms the light-emitting surface of the display device, wherein the bandstop filter is located between the variable wavelength LED and the light-emitting surface of the display device.

47. The method according to any one of claims 43 to 46, comprising the step of: overgrowing the variable wavelength LED over a porous region of a group III nitride material.

48. The method according to any one of claims 42 to 47, wherein the bandstop filter comprises one or more layers of porous group III nitride semiconductor material.

49. The method according to any one of claims 42 to 48, comprising the steps of: forming the bandstop filter by alternating porous group III nitride semiconductor material with porous multiple layers of porous group III nitride material; or forming the bandstop filter by alternating a first multiple layer of porous group III nitride material with a first porosity with a second multiple layer of porous group III nitride material with a second porosity.

Images