Transparent conductive oxide layer with ohmic contact on n-type AlInGaP for LEDs and micro-LEDs

Abstract

AlInGaP LEDs and micro-LEDs (e.g., 600) include a transparent conductive oxide (TCO) layer (620) disposed on and in ohmic contact with an n-type AlInGaP layer (605). The TCO layer can be used to electrically contact the n-type side of the diode junction in the LED without impeding the transmission of light out of the LED through the n-type surface on which the TCO layer is disposed. The TCO layer can improve n-side current spreading. The TCO layer can be used to interconnect n-side contacts of adjacent AlInGaP micro-LEDs in an array (700) to form a shared n-side electrical contact with little or no optical cross-talk. The TCO layer can increase the reflectivity of the n-side metal contact arranged to direct light out of the LED.

Description

[0001] Cross-references to related applications This application claims the benefit of priority to U.S. Patent Application 18 / 397,522, filed December 27, 2023, which is incorporated herein by reference in its entirety. Technical Field

[0002] This invention generally relates to AlInGaP LEDs and microLEDs, as well as arrays, light sources, and displays including AlInGaP LEDs and / or microLEDs. Background Technology

[0003] Light-emitting diodes (LEDs) are among the most efficient light sources available today. The emission spectrum of an LED typically exhibits a single, narrow peak at a wavelength determined by the device's structure and the composition of the semiconductor materials that make it up. By appropriately selecting the device structure and material system, LEDs can be designed to operate in the ultraviolet, visible, or infrared wavelengths.

[0004] LEDs with a maximum size of less than or equal to about 50 micrometers parallel to the layer forming the diode junction are referred to as microLEDs in this paper.

[0005] In the operation of an LED, a forward bias voltage is applied to the diode junction in the LED, and the radiative recombination of injected electrons and holes causes light emission.

[0006] Direct-emission (i.e., non-phosphor-converted) LEDs and microLEDs formed in AlInGaP material systems are high-performance amber and red emitters that can exhibit high external quantum efficiency (EQE), emission peaks with narrow full width at half maximum (FWHM), low-voltage operation, good reliability, and wide color gamut coverage that can be tunable by changing the composition of the light-emitting active region in the device.

[0007] AlInGaP microLEDs can be used as pixel red emitters in applications such as microLED display devices, such as microLED display engines, direct-view displays, and augmented reality (AR), virtual reality (VR), and mixed reality (MR) systems. Such applications can include head-mounted display (HMD) systems. Larger AlInGaP LEDs can operate at high output power and can be used in applications such as traffic lights, automotive (e.g., taillights and / or brake lights), and other lighting applications. Summary of the Invention

[0008] This specification discloses AlInGaP LEDs and microLEDs, which include a transparent conductive oxide layer disposed on and in ohmic contact with an n-type AlInGaP layer. In this specification, an ohmic contact refers to a junction (interface) between the transparent conductive oxide layer and the n-type AlInGaP layer exhibiting a linear current-voltage curve, as per Ohm's law.

[0009] The transparent conductive oxide ohmic contact layer can be formed from, for example, indium tin oxide (ITO) or aluminum-doped zinc oxide (AZO or ZnO:Al). For example, the transparent conductive oxide ohmic contact layer can have a thickness of about 50 angstroms to about 2000 angstroms, typically about 1000 angstroms.

[0010] This transparent conductive oxide ohmic contact layer can be used, for example, for electrical contact with the n-type side of a diode junction in an LED, without obstructing the transmission of light away from the LED through the n-type surface on which the transparent conductive oxide layer is disposed.

[0011] This transparent conductive oxide ohmic contact layer can improve current diffusion on the n-side.

[0012] This transparent conductive oxide layer can be used for n-side contacts of adjacent AlInGaP LEDs or microLEDs in an interconnect array to form shared n-side electrical contacts. Optical crosstalk between adjacent LEDs (where light emitted by one LED appears to originate from another) can be reduced because the transparent conductive oxide layer is very thin compared to the thickness (e.g., 2 to 3 micrometers) of the shared n-type AlInGaP layer, which would otherwise require a shared n-type AlInGaP layer to form such shared n-side electrical contacts.

[0013] The inventors have discovered that if this transparent conductive oxide ohmic contact layer is disposed on an n-type AlInGaP layer, and the metal contact is disposed on a transparent conductive oxide layer opposite the n-type AlInGaP layer, the reflectivity at the interface with the n-type AlInGaP layer is greater than the reflectivity when the metal contact is directly disposed on the n-type AlInGaP layer. Therefore, the transparent conductive oxide ohmic contact layer can be used to improve the mirror function of the n-side metal contact for guiding light away from the LED.

[0014] More generally, this transparent conductive oxide ohmic contact layer can be used to improve optical output power and increase the design flexibility of AlInGaP LEDs and microLEDs.

[0015] Light-emitting diodes incorporating such transparent conductive oxide ohmic contact layers may include, for example, a stack of semiconductor layers, including n-type (Al) semiconductor layers. xn Ga 1-xn ) yn In 1-ynP-layer, p-type (Al) xp Ga 1-xp ) yp In 1-yp P layer and set in n-type (Al) xn Ga 1-xn ) yn In 1-yn P-layer and p-type (Al) xp Ga 1-xp ) yp In 1-yp The active region between P layers. The active region typically includes at least one (Al) xqw Ga 1-xqw ) yqw In 1-yqw The light-emitting diode also includes a p-quantum well layer. The light-emitting diode further includes a transparent conductive oxide contact layer disposed on an n-type (Al) quantum well layer. xn Ga 1-xn ) yn In 1-yn At least a portion of the surface of the P-layer opposite the active region is in ohmic contact with it. The subscripts characterizing the composition of these layers satisfy the following constraints: 0 ≤ xn ≤ 0.6; 0 ≤ yn < 1; 0 ≤ xp ≤ 1; 0 ≤ yp < 1; 0 ≤ xqw ≤ 1; and 0 ≤ yqw < 1.

[0016] As described above, the transparent conductive oxide contact layer can be or includes, for example, an indium tin oxide layer. The transparent conductive oxide contact layer can, for example, have a cross-section perpendicular to the n-type (Al) polarity from about 50 angstroms to about 2000 angstroms. xn Ga 1-xn ) yn In 1-yn Thickness of the P layer.

[0017] Light-emitting diodes (LEDs) can have a maximum dimension parallel to the layers in a stack, for example, greater than about 50 micrometers, greater than or equal to about 100 micrometers, greater than or equal to about 200 micrometers, or greater than or equal to about 500 micrometers. Alternatively, LEDs can be microLEDs with a maximum dimension parallel to the layers in a stack, for example, less than or equal to about 50 micrometers, less than or equal to about 30 micrometers, less than or equal to about 20 micrometers, less than or equal to about 10 micrometers, or less than or equal to about 1 micrometer.

[0018] Display devices may include multiple such LEDs or microLEDs arranged as pixel red emitters, wherein, in addition to the red emitters, pixels in such displays typically include two or more other LEDs emitting other colors (such as blue and green).

[0019] In some variations, the transparent conductive oxide contact layer is only applied to n-type (Al) xnGa 1-xn ) yn In 1-yn The light-emitting diode is located at the center of the surface of the P-layer. In this variation, the light-emitting diode may also include an n-type (Al2O3) diode disposed around the transparent conductive oxide contact layer. xn Ga 1-xn ) yn In 1-yn A transparent dielectric layer is disposed on a portion of the surface of the p-layer, and a second transparent conductive oxide layer is disposed on the transparent dielectric layer and in physical and electrical contact with a transparent conductive oxide ohmic contact layer. Such a light-emitting diode can, for example, be a microLED having the largest dimension parallel to the layers in the stack, such as less than or equal to about 50 micrometers. The light-emitting diode may include, for example, a p-type (Al) layer... xp Ga 1-xp ) yp In 1-yp The metal contact on the central portion of the surface of the P-layer opposite the active region, and the p-type (Al) surrounding the metal contact xp Ga 1-xp ) yp In 1-yp A dielectric layer on a portion of the surface of the P-layer. The light-emitting diode may include, for example, a metal electrical contact disposed on or electrically connected to the second transparent conductive oxide layer, positioned such that it does not impede the passage of light emitted from the active region through the n-type (Al) light-emitting diode. xn Ga 1-xn ) yn In 1-yn Transmission at the P layer.

[0020] The dielectric layer in these devices and the devices described below may be or include, for example, nitride or oxide materials, such as SiO2, TiO2 and SiN. x The composition and thickness of (multiple) dielectric layers can be optimized based on wavelength and performance / reliability requirements. These devices, and the p-metals and n-metals listed below, can be selected based on AlInGaP material and process compatibility.

[0021] An LED array (e.g., a microLED array) may include, for example, at least first and second LEDs, arranged adjacent to each other as in the above variations, and a third transparent conductive oxide layer that is in physical and electrical contact with the second transparent conductive oxide layer on the first LED and with the second transparent conductive oxide layer on the second LED. The third transparent conductive oxide layer, together with the transparent conductive oxide contact layer and the second transparent conductive oxide layer on the first LED and the second transparent conductive oxide layer on the second LED, forms an n-type (Al) LED with respect to the first LED. xn Ga1-xn ) yn In 1-yn P-layer and n-type (Al) of the second light-emitting diode xn Ga 1-xn ) yn In 1-yn A shared transparent conductive oxide contact in the P-layer. In the region between the first and second LEDs, the shared transparent conductive oxide contact can have a shape perpendicular to the n-type (Al) layer. xn Ga 1-xn ) yn In 1-yn The thickness of the P layer is, for example, from about 50 angstroms to about 2000 angstroms, typically 1000 angstroms.

[0022] In some variations, AlInGaP LEDs include those with n-type (Al... xn Ga 1-xn ) yn In 1-yn The surface of the P-layer is in metal contact with the transparent conductive oxide contact layer opposite to and opposite the active region. The transparent conductive oxide contact layer and the metal contact disposed thereon, together with the n-type (Al) xn Ga 1-xn ) yn In 1-yn A reflective interface is formed on the surface of the P layer.

[0023] Metal contact can enable n-type (Al) xn Ga 1-xn ) yn In 1-yn Most of the surface of the p-layer opposite the active region is not blocked, allowing light emitted from the active region to be transmitted. In this variation, the LED may include elements disposed in a p-type (Al) layer. xp Ga 1-xp ) yp In 1-yp A mirror on the surface of the P-layer opposite the active region, occupying most of that surface, and a reflector set in the p-type (Al) xp Ga 1-xp ) yp In 1-yp Metal contacts on a portion of the surface of the P-layer adjacent to the reflector. This LED is configured to transmit through an n-type (Al) xn Ga 1-xn ) yn In 1-yn Light output from the P layer.

[0024] Alternatively, the transparent conductive oxide contact layer, metal contact, and reflective interface extend across the n-type (Al) region opposite the active region. xn Ga1-xn ) yn In 1-yn Most of the p-layer. In this variant, the LED may include a p-type (Al) layer disposed opposite the active region. xp Ga 1-xp ) yp In 1-yp Metal contacts on a portion of the surface of the P-layer, these metal contacts enable p-type (Al) xp Ga 1-xp ) yp In 1-yp Most of the surface of the p-layer is unobstructed for light transmission. This type of LED is configured to transmit light through p-type (Al) layers. xp Ga 1-xp ) yp In 1-yp Light output from the P layer.

[0025] In some variations, the transparent conductive oxide contact layer extends across the n-type (Al) region opposite the active region. xn Ga 1-xn ) yn In 1-yn The entire surface of the P layer, and the n-type (Al) xn Ga 1-xn ) yn In 1-yn The surface of the P-layer does not obstruct the passage of light emitted from the active region through the n-type (Al) layer. xn Ga 1-xn ) yn In 1-yn Metallization of the P-layer transport. Such LEDs may include, for example, those disposed in a laterally extended region beyond the n-type (Al) layer. xn Ga 1-xn ) yn In 1-yn Metal contacts are located on a portion of the transparent conductive oxide contact layer of the P-layer. Alternatively, the LED can be a flip-chip design and include metal contacts disposed on an n-type (Al) layer. xn Ga 1-xn ) yn In 1-yn Metal contacts on the surface of the P-layer opposite to the surface on which a transparent conductive oxide contact layer is disposed, and metal contacts on the p-type (Al) xp Ga 1-xp ) yp In 1-yp Metal contacts on the surface of the P-layer opposite the active region. In this type of LED, the current injected onto the n-side does not pass through the transparent conductive oxide layer, but the transparent conductive oxide contact layer can improve the current diffusion on the n-side.

[0026] The AlInGaP LEDs and microLEDs disclosed herein can be used in various devices and applications, such as those listed above in the Background section.

[0027] These and other embodiments, features, and advantages of the invention will become more apparent to those skilled in the art when taken in conjunction with the accompanying drawings, which have been briefly described above, and in the following more detailed description of the invention. Attached Figure Description

[0028] Figure 1 A schematic cross-sectional view of an example microLED is shown.

[0029] Figure 2A and 2B The cross-sectional view and top view of the microLED array are shown respectively. Figure 2C A schematic top view of a microLED chip is shown, from which such... Figure 2A and 2B The microLED array shown.

[0030] Figure 3A A schematic top view of an electronic board on which a micro-LED array can be mounted is shown, and Figure 3B Similarly, installations are shown. Figure 3A Micro-LED array on an electronic board.

[0031] Figure 4A A schematic cross-sectional view of a microLED array arranged relative to a waveguide or microlens and a projection lens is shown. Figure 4B It shows something similar to Figure 4A The arrangement has no waveguides or microlenses.

[0032] Figure 5 An example display (e.g., AR / VR / MR) system including a microLED array is schematically shown.

[0033] Figure 6 A schematic cross-sectional view of an example vertical thin-film microLED is shown, comprising a transparent conductive oxide layer in ohmic contact with an n-type AlInGaP layer.

[0034] Figure 7 It shows including, for example Figure 6 A schematic cross-sectional view of a portion of an example microLED array, showing two microLEDs.

[0035] Figure 8 A schematic cross-sectional view of an example n-side-up (light emission through this n-side) vertical thin-film light-emitting diode is shown, comprising an ohmic contact of a transparent conductive oxide layer with an n-type AlInGaP layer.

[0036] Figure 9A schematic cross-sectional view of an example p-side-up vertical thin-film light-emitting diode is shown, comprising an ohmic contact between a transparent conductive oxide layer and an n-type AlInGaP layer.

[0037] Figure 10 A schematic cross-sectional view of another example n-side-up (light emission through this n-side) vertical thin-film light-emitting diode is shown, including a transparent conductive oxide layer in ohmic contact with an n-type AlInGaP layer.

[0038] Figure 11 A schematic cross-sectional view of an example AlInGaP flip-chip light-emitting diode is shown, including a transparent conductive oxide layer in ohmic contact with an n-type AlInGaP layer. Detailed Implementation

[0039] The following detailed description should be read with reference to the accompanying drawings, in which the same reference numerals refer to the same elements in different drawings. The drawings, which are not necessarily drawn to scale, depict alternative embodiments and are not intended to limit the scope of the invention. The detailed description illustrates the principles of the invention by way of example rather than limitation.

[0040] Figure 1 An example of a single LED 100 including a light-emitting semiconductor diode (LED) structure 102 disposed on a substrate 104 is shown. The light-emitting semiconductor diode structure 102 typically includes an active region disposed between n-type and p-type layers. Applying a suitable forward bias voltage to the diode structure causes light to be emitted from the active region. The wavelength of the emitted light is determined by the composition and structure of the active region.

[0041] While this specification focuses on direct-emitting AlInGaP LEDs and microLEDs, more generally, direct-emitting and phosphor-converted LEDs and microLEDs (all referred to herein as pcLEDs) can be formed in other material systems, such as, for example, AlInGaN. Typically, pcLEDs comprise a phosphor material that absorbs light from an LED and, in response, emits light of a longer wavelength, forming all or part of the light output from the pcLED. For example, such a pcLED may include an AlInGaN LED emitting ultraviolet or blue light in conjunction with a phosphor. The AlInGaP LEDs and microLEDs disclosed herein can be used in combination with direct-emitting LEDs or microLEDs and / or pcLEDs formed in such other material systems. For example, the red-emitting AlInGaP microLEDs disclosed herein can be used in combination with direct-emitting AlInGaN microLEDs or phosphor-converted microLEDs (pcmicroLEDs) emitting blue or green light to form RGB pixels of a display.

[0042] Figure 2A-2BCross-sectional and top views of an array 200 of LEDs 100 disposed on a substrate 202 are shown, respectively. Such an array can include any suitable number of LEDs arranged in any suitable manner. In the example shown, the array is described as being monolithically formed on a shared substrate; however, alternatively, the LED array can be formed from separate individual LEDs. The substrate 202 may optionally include CMOS circuitry for driving the microLEDs and can be formed from any suitable material.

[0043] although Figure 2A-2B A 3×3 array of 9 LEDs is shown, but such an array can include, for example, dozens, hundreds, or thousands of LEDs. The width (e.g., side length) of a single LED in the array plane can be less than or equal to 1 millimeter (mm), less than or equal to 500 micrometers, less than or equal to 100 micrometers, less than or equal to 50 micrometers, less than or equal to 30 micrometers, less than or equal to 10 micrometers, or less than or equal to 1 micrometer.

[0044] The LEDs in such an array can be separated from each other by streets or channels having a width of, for example, several hundred micrometers, less than or equal to 100 micrometers, less than or equal to 50 micrometers, less than or equal to 30 micrometers, less than or equal to 10 micrometers, or less than or equal to 5 micrometers in the array plane. Although the example shown depicts rectangular microLEDs arranged in a symmetrical matrix, the microLEDs and the array can have any suitable shape or arrangement. Although the example shown depicts an array in which all microLEDs are the same size, the sizes of the microLEDs in the array can be different.

[0045] Furthermore, as mentioned above, such an array may include LEDs formed from different material systems and emitting different colors of light and / or include pc microLEDs.

[0046] Figure 2C A schematic top view of a portion of a microLED chip 210 (e.g., an AlInGaP LED chip) is shown, from which such... Figure 2A and 2B The LED array shown. Figure 2CAn enlarged 3×3 section of the wafer is also shown. In the example wafer, individual LEDs 111 with side lengths (e.g., width) W1 are arranged in a square matrix, adjacent LEDs having a center-to-center distance D1 and separated by channels 113 of width W2. W1 can be, for example, less than or equal to 1 millimeter (mm), less than or equal to 500 micrometers, less than or equal to 100 micrometers, less than or equal to 50 micrometers, less than or equal to 30 micrometers, less than or equal to 10 micrometers, less than or equal to 5 micrometers, or less than or equal to 1 micrometer. W2 can be, for example, several hundred micrometers, less than or equal to 100 micrometers, less than or equal to 50 micrometers, less than or equal to 10 micrometers, or less than or equal to 5 micrometers. D1 = W1 + W2.

[0047] For example, an array can be formed by dividing the wafer 210 into individual LEDs and arranging the LEDs on a substrate (e.g., in combination with LEDs or microLEDs and / or pcLEDs or pcmicroLEDs formed in other material systems). Alternatively, the array can be formed from the entire wafer 210, or by dividing the wafer 210 into smaller arrays of LEDs.

[0048] As mentioned above, LEDs or pcLEDs with dimensions (e.g., side length) less than or equal to about 50 micrometers in the array plane are generally referred to as microLEDs, and arrays of such microLEDs can be referred to as microLED arrays.

[0049] Each LED or pcLED in the array can be individually operable (addressable) and / or can operate as part of a group or subset (e.g., adjacent) of LEDs or pcLEDs in the array. A single individually operable LED or pcLED, or a group of adjacent such LEDs and / or pcLEDs, can correspond to a single pixel (image element) in the display. For example, a group of three individually operable adjacent LEDs and / or pcLEDs, including a red emitter, a blue emitter, and a green emitter, can correspond to a single color-tunable pixel in the display.

[0050] like Figures 3A-3B As shown, the LED array 200 can be mounted, for example, on an electronic board 300, which includes a power and control module 302, a sensor module 304, and an attachment area 306. The power and control module 302 can receive power and control signals from an external source and signals from the sensor module 304, based on which it controls the operation of the LEDs and / or pcLEDs in the array. The sensor module 304 can receive signals from any suitable sensor, such as a temperature or light sensor. Alternatively, the array 200 can be mounted on a separate board (not shown) from the power and control module and the sensor module.

[0051] like Figure 4A As shown, a single LED or pcLED may optionally include a lens (e.g., a microlens for a microLED or pcMicroLED) or other optical elements, or be arranged in combination with a lens (e.g., a microlens for a microLED or pcMicroLED) or other optical elements, the lens (e.g., a microlens for a microLED or pcMicroLED) or other optical elements being located near or disposed on the phosphor layer of the LED or pcLED. Furthermore, as... Figures 4A-4B As shown, array 200 (e.g., mounted on electronic board 300) can be arranged in conjunction with light-collecting optics or optical systems (e.g., projection lens 404). Figure 4A In this configuration, light emitted by the LED and / or pcLED 100 is collected by a waveguide or lens (e.g., a microlens) 402 and guided to a projection lens 404. For example, the projection lens 404 could be a Fresnel lens. Figure 4B In this configuration, the light emitted by the LEDs and / or pcLEDs 100 is directly collected by the projection lens 404 without the use of intermediate optics. This arrangement may be particularly suitable when the LEDs or pcLEDs can be spaced sufficiently close to each other. For example, microLED display applications may use a similar arrangement. Figures 4A-4B The optical arrangement is shown. Typically, any suitable arrangement of optical elements can be used in conjunction with the array described herein, depending on the desired application.

[0052] Figure 5 An example display (e.g., AR / VR / MR) system 500 is schematically illustrated, comprising a micro-LED and / or pc-microLED array 510, a display 520, a light-emitting array controller 530, a sensor system 540, and a system controller 550. Control inputs are provided to the sensor system 540, while power and user data inputs are provided to the system controller 550. In some embodiments, the modules included in the system 500 may be compactly arranged in a single structure, or one or more components may be mounted separately and connected via wireless or wired communication. For example, the light-emitting array 510, display 520, and sensor system 540 may be mounted on a headset or glasses, with the light-emitting controller and / or system controller 550 mounted separately. The system 500 may incorporate various optics in the light-emitting array 510 and / or display 520, for example, coupling light emitted by the light-emitting array 510 to the display 520.

[0053] Sensor system 540 may include external sensors such as cameras, depth sensors, or audio sensors to monitor the environment, and internal sensors such as accelerometers or two-axis or three-axis gyroscopes to monitor the position of the AR / VR / MR headset. In some embodiments, control input may include detected touch or tap, gesture input, or control based on the position of the headset or display.

[0054] In response to data from sensor system 540, system controller 550 can send images or commands to light-emitting array controller 530. Images or commands can also be changed or modified via user data input or as needed automatic data input. User data input can include, but is not limited to, data input provided by audio commands, haptic feedback, eye or pupil positioning, or a connected keyboard, mouse, or game controller.

[0055] As summarized above, this specification discloses AlInGaP LEDs and microLEDs comprising a transparent conductive oxide layer disposed on and in ohmic contact with an n-type AlInGaP layer. Forming a transparent conductive oxide layer in ohmic contact with an n-type AlInGaP layer is inherently difficult due to the electronic band structure and doping of the n-type AlInGaP layer. The inventors have discovered that such a transparent conductive oxide ohmic contact layer can be formed on an n-type AlInGaP layer by appropriately selecting the amount of aluminum in the layer (which affects the band structure) and appropriately selecting the n-type dopant density. Generally, the lower the aluminum content, the easier it is to form an ohmic contact between the transparent conductive oxide layer and the n-type AlInGaP layer. For LEDs with a composition (Al... xn Ga 1-xn ) yn In 1-yn An n-type layer of the p-type layer can form an ohmic contact, for example, for 0 ≤ xn ≤ 0.6, depending in part on the dopant density used. The n-type dopant can be, for example, silicon. For example, 3 × 10⁻⁶ 17 / (cm) 3 ≤[Si]≤5×10 18 / (cm) 3 The silicon dopant density can form an ohmic contact between the transparent conductive oxide layer and the n-type AlInGaP layer, which depends in part on the aluminum content in the layer.

[0056] Typically, the process for forming a transparent conductive oxide layer that provides an ohmic contact with an n-type AlInGaP layer includes the following steps. First, an n-type AlInGaP layer with a suitable aluminum content and a suitable n-type dopant density is formed. The aluminum content is typically chosen to promote an ohmic contact and can also depend on the desired emission wavelength of the light-emitting diode. Next, the surface on which the transparent conductive oxide layer will be deposited is cleaned, for example, using a wet etching or dry etching process. Next, a transparent conductive oxide layer (e.g., indium tin oxide) is deposited on the surface of the n-type AlInGaP layer. This can be accomplished, for example, using electron beam evaporation, RF sputtering, ion beam sputtering, or atomic layer deposition (ALD) with or without plasma. Typically, the deposited transparent conductive oxide layer does not provide an ohmic contact with the n-type AlInGaP layer. An annealing process is typically required to achieve the ohmic contact. Depending on the thickness of the transparent conductive oxide layer, the aluminum content of the AlInGaP layer, and the concentration of the n-type dopant in the AlInGaP layer, the annealing temperature can be, for example, from about 300°C to about 475°C. Typically, as the annealing temperature increases, the ohmic contact improves and the resistance of the ohmic contact decreases.

[0057] The following description Figures 6 to 11 Example AlInGaP LEDs and microLED devices are shown, which incorporate a transparent conductive oxide layer in ohmic contact with an n-type AlInGaP layer. These devices typically emit light with peak wavelengths from about 580 nm to about 660 nm, such as 630 nm or 650 nm, depending primarily on the structure and composition of one or more quantum wells in their light-emitting active region. Limitations on the subscripts characterizing the composition of the various materials in these devices have been given in the above-described invention section.

[0058] Figure 6 A schematic cross-sectional view of an example vertical thin-film microLED 600 is shown. The microLED 600 includes n-type (Al)... xn Ga 1-xn ) yn In 1-yn P-layer 605, p-type (Al) xp Ga 1-xp ) yp In 1-yp A p-layer 610 and an active region 615 disposed between the n-type layer 605 and the p-type layer 610. The active region typically includes at least one (Al) xqw Ga 1-xqw ) yqw In 1-yqwA p-quantum well layer (not shown). The micro-LED 600 includes a transparent conductive oxide ohmic contact layer 620 disposed on a central portion of the surface of an n-type layer 605. A transparent dielectric layer 625 disposed on a portion of the surface of the n-type layer surrounds the transparent conductive oxide ohmic contact layer 620. A second transparent conductive oxide layer 630 is disposed on the transparent dielectric layer 625 and is in physical and electrical contact with the transparent conductive oxide ohmic contact layer 620. For example, the transparent conductive oxide layers 620 and 630 may be formed of the same transparent conductive oxide and may be formed as a single continuous layer, with reference numerals 620 and 630 indicating different portions of the same layer.

[0059] A metal electrical contact 632 is disposed on or electrically connected to the second transparent conductive oxide layer 630, positioned such that it does not obstruct the transmission of light emitted from the active region through the n-type layer. A metal electrical contact 635 is disposed on the central portion of the surface of the p-type layer 610 opposite the active region. A dielectric layer 640 is disposed on a portion of the surface of the p-type layer surrounding the metal contact 635, and an additional dielectric layer 640 may coat the sidewalls of the device.

[0060] When a suitable forward voltage is applied across contacts 632 and 635, the microLED emits light through the n-type layer, the transparent conductive oxide layer, and the transparent dielectric layer, as indicated by the central vertical arrow in the figure. This arrangement allows for high light extraction efficiency from the microLED because no metal contacts are required to block light transmission away from the n-type layer. This is particularly important for microLEDs, as metal contacts with the n-type layer can impede a significant portion of the relatively small (e.g., 50 μm × 50 μm) surface area of ​​the n-type layer. For example, microLED 600 can be used in direct-view microLED displays.

[0061] Figure 7 A schematic cross-sectional view of a portion of a microLED array 700 is shown, which includes two such microLED arrays arranged adjacent to each other. Figure 6 The microLEDs are shown. Array 700 also includes a transparent conductive oxide layer 710 disposed between two microLEDs, which is in physical and electrical contact with a transparent conductive oxide layer 630 on the two microLEDs. Transparent conductive oxide layers 710, 630, and 620 together form a shared transparent conductive oxide contact to the n-type layer of the two microLEDs. For example, transparent conductive oxide layers 710, 630, and 620 may be formed of the same transparent conductive oxide and may be formed as a single continuous layer, with reference numerals 710, 620, and 630 indicating different portions of the same layer.

[0062] like Figure 7As shown, a transparent conductive oxide 720 can be formed on and electrically contacted with the n-side metal electrode 715, which transmits current to other microLEDs in the array located behind those microLEDs shown in the figure.

[0063] In the region between the first and second LEDs, the shared transparent conductive oxide n-side contact can have a thickness perpendicular to the n-type layer, for example, from about 50 angstroms to about 2000 angstroms. This is thin enough (e.g., significantly smaller than the wavelength of light emitted by the microLEDs) that little or no light leaks from one microLED to an adjacent microLED through the shared transparent conductive oxide n-side contact. Therefore, this arrangement minimizes optical crosstalk between adjacent microLEDs.

[0064] The microLED array 700 can be used in microLED displays, such as augmented reality displays.

[0065] Figure 8-11 The diagram schematically illustrates an LED with the largest dimension parallel to the layers in the stack, for example, greater than or equal to about 100 micrometers, greater than or equal to about 200 micrometers, greater than or equal to about 500 micrometers, or greater than or equal to about 1 millimeter. Such an LED can be used in applications such as traffic lights, automotive taillights (e.g., brake lights), and other lighting applications.

[0066] Figure 8 A schematic cross-sectional view of an example n-side-up (emitting light through the n-side) vertical thin-film light-emitting diode 800 is shown. Figure 9 A schematic cross-sectional view of an example p-side-up (emitting light via the p-side) vertical thin-film light-emitting diode 900 is shown. (See reference above.) Figure 6 and Figure 7 The light-emitting diodes described, 800 and 900, include an n-type AlInGaP layer 605, a p-type AlInGaP layer 610, an AlInGaP active region 615, and a transparent conductive oxide ohmic contact layer 620 disposed on the n-type AlInGaP layer.

[0067] Example LED 800 includes an n-side metal contact 805 disposed on a transparent conductive oxide ohmic contact layer 620. Example LED 900 similarly includes an n-side metal contact 905 disposed on a transparent conductive oxide ohmic contact layer 620. As described above, the inventors have discovered that metal contacts disposed on a transparent conductive oxide ohmic contact layer (such as...) Figure 8 and Figure 9(As shown) a better reflectivity is provided at the n-type AlInGaP interface than a metal contact directly disposed on the n-type AlInGaP layer. This is because the interface including a transparent conductive oxide ohmic contact layer is smoother than an interface formed directly between the metal contact and the n-type AlInGaP layer. The smoother interface with the transparent conductive oxide ohmic contact layer is due to the transparent conductive oxide layer reducing the interdiffusion between the metal contact and the n-type AlInGaP layer. This interdiffusion roughens the interface, promotes scattering and absorption, and reduces specular reflection.

[0068] The example light-emitting diode 800 includes a p-side metal contact and a p-side reflector 815, which occupies most of the p-side surface and forms the back reflector of the device. An n-side metal contact 805 allows most of the n-type AlInGaP surface to be unobstructed for light transmission. Furthermore, due to the high reflectivity at the n-type AlInGaP interface beneath the n-side metal contact, light incident on this interface can be efficiently reflected toward the p-side reflector 815 and then reflected through the stack of layers and exits the device through the n-type AlInGaP layer (as indicated by the arrows in the figure). This improves the device efficiency compared to n-side-up vertical thin-film light-emitting diodes lacking a transparent conductive oxide ohmic contact layer.

[0069] In the example LED 900, a transparent conductive oxide ohmic contact layer 620 and an n-side metal contact 905 extend across most of the n-type AlInGaP surface to form a highly reflective back mirror. Light incident on the AlInGaP interface beneath the n-side metal contact can be reflected back through the stack of layers and exit the device through the p-type AlInGaP layer (as indicated by the arrows in the figure). The p-side metal contact 910 leaves most of the p-side layer surface unobstructed for light transmission away from the device.

[0070] Figure 10 A schematic cross-sectional view of another example n-side-up (emitting light via the n-side) vertical thin-film light-emitting diode 1000 is shown. In the LED 1000, a transparent conductive oxide ohmic contact layer 620 extends across the entire surface of the n-type layer opposite the active region, and the surface of the n-type layer may be free of any metallization (e.g., fingers) that obstructs the transmission of light emitted from the active region through the n-type layer. The LED 1000 includes an n-side metal contact 1005 disposed on a portion of the transparent conductive oxide contact layer extending laterally beyond the n-type AlInGaP layer. The LED 1000 is otherwise similar to the LED 800 described above. Reducing or eliminating n-side metallization on the output surface of the n-type AlInGaP layer in this manner improves light extraction from the device.

[0071] Figure 11A schematic cross-sectional view of an example AlInGaP flip-chip light-emitting diode 1100 is shown. As in the described light-emitting diode, the flip-chip light-emitting diode 1100 includes an n-type AlInGaP layer 605, a p-type AlInGaP layer 610, an AlInGaP active region 615, and a transparent conductive oxide ohmic contact layer 620 disposed on the surface of the n-type AlInGaP layer. The light-emitting diode 1100 also includes a metal contact 1105 disposed on the surface of the n-type layer opposite to the surface on which the transparent conductive oxide layer is disposed, and a metal contact 1110 disposed on the surface of the p-type layer opposite to the active region. Current injected into the n-side of the light-emitting diode 1100 does not pass through the transparent conductive oxide layer; however, the transparent conductive oxide contact layer improves the current diffusion on the n-side because it provides a low-resistance path for the current to move laterally parallel to the n-type layer and then return to the n-type layer. As indicated by the arrows in the figure, light emission from this device passes through the n-type layer 605 and the transparent conductive oxide ohmic contact layer 620.

[0072] This disclosure is illustrative and not restrictive. Further modifications based on this disclosure will be apparent to those skilled in the art and are intended to fall within the scope of the appended claims.

Claims

1. A light-emitting diode, comprising: The stacking of semiconductor layers, including n-type (Al) xn Ga 1-xn ) yn In 1-yn P layer; p-type (Al) xp Ga 1-xp ) yp In 1-yp P layer; and The active region is set in the n-type (Al) region. xn Ga 1-xn ) yn In 1-yn P-layer and p-type (Al) xp Ga 1-xp ) yp In 1-yp Between P layers and including at least one (Al) xqw Ga 1-xqw ) yqw In 1-yqw P quantum well layer; and Transparent conductive oxide contact layer, set in n-type (Al) xn Ga 1-xn ) yn In 1-yn On at least a portion of the surface of the P layer opposite the active region and in ohmic contact with it; in 0 ≤ xn ≤ 0.6; 0≤yn<1; 0≤xp≤1; 0≤yp<1; 0≤xqw≤1; and 0≤yqw<1.

2. The light-emitting diode according to claim 1, wherein the transparent conductive oxide contact layer is or includes an indium tin oxide layer.

3. The light-emitting diode according to claim 1, wherein the transparent conductive oxide contact layer has a shape perpendicular to the n-type (Al) type. xn Ga 1-xn ) yn In 1-yn The P layer has a thickness of approximately 50 angstroms to approximately 2000 angstroms.

4. The light-emitting diode according to claim 1, wherein the transparent conductive oxide contact layer is disposed only in the n-type (Al) diode. xn Ga 1-xn ) yn In 1-yn The central portion of the surface of layer P includes: A transparent dielectric layer is disposed around the transparent conductive oxide contact layer of type n (Al). xn Ga 1-xn ) yn In 1-yn On a portion of the surface of the P layer; and A second transparent conductive oxide layer is disposed on the transparent dielectric layer and is in physical and electrical contact with the transparent conductive oxide contact layer.

5. The light-emitting diode according to claim 4, wherein the n-type (Al) xn Ga 1-xn ) yn In 1-yn The maximum size of the P layer, which is parallel to the layer and opposite to the active region, is less than or equal to about 50 micrometers.

6. The light-emitting diode according to claim 5, comprising: Metal contacts are only provided in the p-type (Al) region opposite to the active region. xp Ga 1-xp ) yp In 1-yp On the central portion of the surface of layer P; and A dielectric layer is disposed around the p-type (Al) contact. xp Ga 1-xp ) yp In 1-yp On a portion of the surface of the P layer.

7. The light-emitting diode according to claim 5, comprising a metal contact disposed on or electrically connected to the second transparent conductive oxide layer, the metal contact not obstructing light emitted from the active region from passing through the (Al) layer. xn Ga 1-xn ) yn In 1-yn Transmission at the P layer.

8. A display device comprising a plurality of LEDs as claimed in claim 5, configured and arranged as pixel red emitters.

9. A light-emitting micro-LED array, comprising: At least first and second light-emitting diodes arranged adjacent to each other, wherein the light-emitting diodes are the light-emitting diodes as described in claim 5; and The third transparent conductive oxide layer is in physical and electrical contact with the second transparent conductive oxide layer on the first light-emitting diode, and is also in physical and electrical contact with the second transparent conductive oxide layer on the second light-emitting diode. The third transparent conductive oxide layer, together with the transparent conductive oxide contact layer and the second transparent conductive oxide layer on the first light-emitting diode, and the transparent conductive oxide contact layer and the second transparent conductive oxide layer on the second light-emitting diode, form an n-type (Al) junction with the first light-emitting diode. xn Ga 1-xn ) yn In 1-yn P-layer and n-type (Al) of the second light-emitting diode xn Ga 1-xn ) yn In 1-yn Shared transparent conductive oxide contacts in the P-layer.

10. The light-emitting microLED array of claim 9, wherein in the region between the first light-emitting diode and the second light-emitting diode, the shared transparent conductive oxide contact has a shape perpendicular to the n-type (Al) type. xn Ga 1-xn ) yn In 1-yn The P layer has a thickness of approximately 50 angstroms to approximately 2000 angstroms.

11. The light-emitting microLED array of claim 9, wherein at least the first and second light-emitting diodes each comprise: Metal contacts are provided in the p-type (Al) region opposite to the active region. xp Ga 1-xp ) yp In 1-yp On the central portion of the surface of layer P; and A dielectric layer is disposed around the p-type (Al) contact. xp Ga 1-xp ) yp In 1-yp On a portion of the surface of the P layer.

12. The light-emitting microLED array according to claim 9, comprising a metal contact disposed on or electrically connected to the shared transparent conductive oxide contact, the metal contact not obstructing light emitted from the active region from passing through the first or second light-emitting diode (Al). xn Ga 1-xn ) yn In 1-yn Transmission at the P layer.

13. The light-emitting diode according to claim 1, comprising a component disposed in relation to the n-type (Al) light-emitting diode. xn Ga 1-xn ) yn In 1-yn The surface of the P layer is in contact with the metal on the transparent conductive oxide contact layer opposite to and opposite to the active region. The transparent conductive oxide contact layer and the metal contact thereon are together with the n-type (Al) xn Ga 1-xn ) yn In 1-yn A reflective interface is formed on the surface of the P layer.

14. The light-emitting diode of claim 13, wherein the metal contact causes the n-type (Al) opposite the active region to... xn Ga 1-xn ) yn In 1-yn Most of the surface of the P layer is unobstructed, allowing light emitted from the active region to be transmitted.

15. The light-emitting diode according to claim 14, comprising: The reflector is set in the p-type (Al) xp Ga 1-xp ) yp In 1-yp The P-layer occupies most of the surface opposite the active region; and Metal contact, provided in the p-type (Al) xp Ga 1-xp ) yp In 1-yp On the surface of layer P, on the portion adjacent to the reflector.

16. The light-emitting diode of claim 1, wherein the transparent conductive oxide contact layer, the metal contact, and the reflective interface extend across the n-type (Al) region opposite the active region. xn Ga 1-xn ) yn In 1-yn Most of the P layer.

17. The light-emitting diode according to claim 16, wherein the metal contact is disposed in the p-type (Al) diode. xp Ga 1-xp ) yp In 1-yp On a portion of the surface of the P-layer opposite the active region, the metal contact enables the p-type (Al) xp Ga 1-xp ) yp In 1-yp Most of the surface of the P-layer is unobstructed, allowing for light transmission.

18. The light-emitting diode of claim 1, wherein the transparent conductive oxide contact layer extends across the n-type (Al2O3) region opposite the active region. xn Ga 1-xn ) yn In 1-yn The entire surface of the P layer, and without any obstruction to the passage of light emitted from the active region through the n-type (Al) layer. xn Ga 1-xn ) yn In 1-yn Metallization of transmission in the P layer.

19. The light-emitting diode of claim 18, comprising a component disposed in the transparent conductive oxide contact layer extending laterally beyond the n-type (Al) type. xn Ga 1-xn ) yn In 1-yn Metal contacts on a portion of the P layer.

20. The light-emitting diode according to claim 18, comprising: Set in the n-type (Al) xn Ga 1-xn ) yn In 1-yn Metal contact on the surface of layer P opposite to the transparent conductive oxide contact layer; and Set in the p-type (Al) xp Ga 1-xp ) yp In 1-yp Metal contact on the surface of the P layer opposite to the active region.

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