LED device and method for manufacturing an LED device

Abstract

The light-emitting diode (LED) includes an n-doped section, a p-doped section, and a light-emitting region disposed between the n-doped section and the p-doped section. The light-emitting region includes a light-emitting layer that emits light at a peak wavelength between 400 and 599 nm under an electrical bias, a III-nitride layer disposed on the light-emitting layer, and a III-nitride barrier layer disposed on the III-nitride layer. The light-emitting diode includes a porous region of III-nitride material. Arrays of LEDs and methods for fabricating LEDs having a peak emission wavelength between 400 and 599 nm under an electrical bias are also provided.

Description

[Technical Field]

[0001] This invention relates to light-emitting diodes (LEDs) and improved manufacturing methods for LEDs. [Background technology]

[0002] III-V semiconductor materials, particularly the group of III nitride semiconductor materials, are extremely important in semiconductor device design.

[0003] III-V semiconductors include binary, ternary, and quaternary alloys of Group III elements such as Ga, Al, and In, and Group V elements such as N, P, As, and Sb, and are important in various application fields, including optoelectronics.

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

[0005] For optoelectronic semiconductor devices, doping GaN semiconductor material with indium (Indium) is of interest. This is because variations in the In content of a semiconductor change the material's electron bandgap, and therefore the emission wavelength of the semiconductor. However, variations in the In content also affect the in-plane lattice constant of the semiconductor. For example, the in-plane lattice constant of InN is approximately 11% larger than that of GaN, and the lattice dimensions of the intermediate composition vary depending on the indium content. Therefore, when it is desired to deposit an active semiconductor layer on a substrate layer with different lattice dimensions, device design problems arise. This is because lattice mismatch at the layer boundary generates strain within the lattice, which in turn forms defects in the material that act as non-radiative recombination centers. This significantly impairs device performance.

[0006] There is a very large demand for LEDs that emit light at all visible wavelengths, especially at long wavelengths close to green, yellow, and red. However, manufacturers have historically faced many problems in the manufacture of LEDs that emit light at long wavelengths.

[0007] One of the major challenges associated with growing long-wavelength LEDs such as green LEDs, yellow LEDs, and red LEDs on a GaN-based platform is that, for example, in order to reduce the bandgap of the active region to a level suitable for long-wavelength emission, it is necessary to increase the indium (In) content. The required InGaN active region has a larger lattice parameter than the underlying GaN, and the resulting strain forms defects that act as non-radiative recombination centers within the material, degrading device performance.

[0008] Therefore, due to the large lattice mismatch between InN and GaN, it is difficult to achieve high-quality InGaN (with an indium content higher than 20%). Also, the mismatch strain leads to a reduction in indium composition due to the composition pulling effect.

[0009] Short-wavelength LEDs can be more easily manufactured because they can be fabricated using an InGaN light-emitting region with a lower indium content than that required for long-wavelength emission. SUMMARY OF THE INVENTION

[0010] The present invention relates to an improved method for manufacturing LEDs and to LEDs manufactured using that method.

[0011] The present invention is defined in the independent claims, which are hereby incorporated by reference. Preferred or advantageous features of the present invention are described in the appended subclaims.

[0012] The light-emitting diodes, or LEDs, described in this application are preferably formed from a III-V semiconductor material, and particularly preferably from a III nitride semiconductor material.

[0013] Group III-V semiconductors include binary, ternary, and quaternary alloys of Group III elements such as Ga, Al, and In, and Group V elements such as N, P, As, and Sb, and are important in numerous applications, including optoelectronics.

[0014] Of particular importance are the semiconductor material class 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, and (Al,In)GaN. In this invention, various crystal orientations can be used, including polar c-planes, nonpolar, and semipolar orientations. Two main nonpolar orientations are the a-plane (11-20) and the m-plane (1-100). Semipolar orientations include (11-22) and the crystal plane group {2021}. Group III nitride materials have not only achieved commercial success in semiconductor lighting and power electronics, but also have special advantages in quantum light sources and light-matter interactions.

[0015] While a wide variety of Group III nitride materials are commercially interesting, gallium nitride (GaN) is widely recognized as one of the most important new semiconductor materials and is particularly important in numerous applications.

[0016] It is known that introducing pores into bulk group III nitrides such as GaN significantly affects their material properties (optical, mechanical, electrical, and thermal). Therefore, porous GaN is of interest to optoelectronic applications because it may be possible to adjust various material properties of GaN and group III nitride semiconductors by changing the porosity.

[0017] The present invention is described with reference to GaN and InGaN, but is also advantageously applicable to alternative combinations of Group III nitride materials.

[0018] In the following description, the growth substrate is a semiconductor structure, and further semiconductor layers are grown on it to form a semiconductor device. An exemplary growth substrate in the present invention is a GaN semiconductor structure comprising multiple layers of doped GaN and undoped GaN.

[0019] The layers of the semiconductor structure can be made porous by electrochemical etching, as described in international patent applications PCT / GB2017 / 052895 (published as WO2019 / 063957) and PCT / GB2019 / 050213 (published as WO2019 / 145728).

[0020] The inventors have found that LEDs can be provided advantageously using the present invention.

[0021] LED According to a first aspect of the present invention, a light-emitting diode (LED) is provided. This LED is n-doped section and, p-doped section, It includes an luminescent region positioned between the n-doped and p-doped regions, and the luminescent region is A light-emitting layer that emits light at a peak wavelength of 400-599 nm under electrical bias, It includes a group III nitride layer disposed on a light-emitting layer and a group III nitride barrier layer disposed on the group III nitride layer, The LED includes a porous region of a group III nitride material.

[0022] The inventors have recognized that electrochemical porosity of Group III nitride materials favorably reduces strain within the Group III nitride lattice and warping or bending of the wafer as a whole. While we do not wish to be bound by theory, it is thought that the process of porosizing the porous regions of Group III nitride materials also etches away structural defects, such as threading dislocations, that formed during the growth of layers on top of the first Group III nitride material layer.

[0023] When dislocations are removed from the semiconductor material in the porous region during porosity formation, strain within the porous region is significantly reduced, especially when the lattice dimensions of the porous region do not match those of the underlying material. Therefore, when a group III nitride material layer is deposited above a porous region, the porous material becomes more easily aligned with the lattice of the non-porous layer superimposed on it during the epitaxial growth of the semiconductor structure. As a result, the strain in the layer above the porous region is significantly lower compared to the case where the porous region is absent.

[0024] As the strain of the second group III nitride material decreases, the number of structural defects in the non-porous layer that act as non-radiative recombination centers that impair device performance also decreases.

[0025] Compositional Entrapment Effect: Kawaguchi et al. reported a so-called InGaN compositional entrapment effect, in which the proportion of indium is small in the early stages of growth but increases with increasing growth thickness. This observation was, to some extent, independent of the underlying GaN or AlGaN. The authors suggested that this effect arises from strain caused by lattice mismatch at the interface. The authors found that as the lattice mismatch between InGaN and the lower epitaxial layer increases, the change in In content becomes larger.

[0026] According to "Theoretical study of the composition pulling effect in InGaN metalorganic vapor-phase epitaxy growth" by Inatomi et al. (Japanese Journal of Applied Physics, Volume 56, Number 7), compressive strain was found to suppress InN uptake. On the other hand, tensile strain promotes InN uptake compared to relaxed bulk growth.

[0027] The inventors have found that using porous regions in a semiconductor structure results in "strain relaxation," which reduces strain within the layers of the semiconductor structure, potentially leading to improvements in terms of compositional incorporation effects. Porous formation reduces strain within the group III nitride layer, resulting in less strain in the semiconductor structure, thus creating conditions for incorporating more indium. Therefore, the present invention can facilitate the incorporation of more indium into the layers of an LED structure grown on a porous region, which is highly desirable for long-wavelength emission.

[0028] The n-doped region, the light-emitting region, and the p-doped region are preferably provided above the porous region. In other words, the porous region is positioned below the n-doped region, the light-emitting region, and the p-doped region of the LED structure.

[0029] The light-emitting layer is preferably an indium gallium nitride (InGaN) layer.

[0030] By incorporating a porous region of Group III nitride material into the LED, n-doped regions, light-emitting regions, and p-doped regions can be grown on the porous region with less strain than would be possible without the porous region. Therefore, reducing the strain level of such a multilayer semiconductor structure helps to incorporate a large amount of indium into one or more light-emitting layers of the LED, making it possible to grow a high-quality InGaN light-emitting layer with a high indium content. As a result, sufficient indium can be incorporated into the light-emitting indium gallium nitride layer, and the LED emits light at a peak wavelength of 400-599 nm when an electrical bias is applied.

[0031] As mentioned in the background technology section above, there is a very large demand for red LEDs that emit light in the 400-599nm range, but it has been difficult to achieve long-wavelength LEDs due to technical difficulties in incorporating sufficient indium into one or more light-emitting layers.

[0032] The light-emitting layer emits light at peak wavelengths of 400-599 nm, 400-590 nm, or 430-570 nm under electrical bias.

[0033] The inventors discovered that when an LED structure is grown on a porous region of a group III nitride material, the emission wavelength shifts significantly to longer wavelengths compared to when the same LED structure is grown on a non-porous substrate.

[0034] To demonstrate this, the inventors grew a conventional green (500-520nm emission) InGaN LED structure on a non-porous GaN wafer and confirmed that this LED emitted green light as expected. Next, they grew the same "green" InGaN LED structure on a template containing porous regions, and when an electrical bias was applied to this LED, the LED emitted light in a longer (redshifted) wavelength range of 530-550nm.

[0035] To demonstrate a similar redshift, a conventional blue LED was grown on GaN, and as expected, it emitted light at a peak wavelength of approximately 435 nm. Next, the same LED structure was grown on a template containing porous regions, but this LED emitted light at a peak emission wavelength of 450–460 nm.

[0036] Therefore, the present invention allows for the shift of conventional, easily manufactured LED structures to long-wavelength emission. This means that LEDs previously used as short-wavelength (e.g., violet or blue) LEDs can be converted into long-wavelength LEDs by incorporating porous regions into their structure. This allows for the advantageous fabrication of LEDs without generating many of the technical problems associated with the design of conventional technologies.

[0037] Conventionally, growing InGaN quantum wells incorporating the large amount of indium necessary for long-wavelength emission required low growth temperatures during the epitaxial growth of the InGaN material. Disadvantages of low growth temperatures include the presence of many defects in the crystal structure and low NH3 cracking efficiency.

[0038] However, in this invention, the presence of porous regions in the LED template during growth reduces strain on the crystal structure, allowing more In to be incorporated into the active region at a given growth temperature than previously possible. Therefore, since a large amount of In is incorporated at high temperatures by incorporating porous regions into the structure, it is no longer necessary to lower the InGaN growth temperature to increase In incorporation. This makes it possible to use high InGaN growth temperatures for LEDs, resulting in improved crystal quality, reduced defects, and improved performance and LED characteristics compared to LEDs of similar wavelengths in the prior art.

[0039] The LED light-emitting region is preferably an LED light-emitting region that emits light at a peak wavelength lower than the peak emission wavelength of the LED, and the porous region of the group III nitride material shifts the peak emission wavelength of the light-emitting region to a longer peak emission wavelength.

[0040] The magnitude of redshift caused by the porous region beneath the LED structure depends on many factors, including the porosity and thickness of the porous region and the design of the LED active region. A variety of LED active regions are known to those skilled in the art, and varying the epitaxial design (thickness, composition, doping level) is common in state-of-the-art technology.

[0041] The magnitude of the redshift varies across different LED structures, but in a preferred embodiment, the typical wavelength redshift generated by porous regions is 15 nm to 80 nm, preferably 15 nm to 50 nm, particularly preferably 30 nm to 50 nm, or 30 nm to 40 nm. Therefore, conventional LED structures grown on non-porous GaN substrates emit light at a peak emission wavelength 15 to 80 nm, 15 to 50 nm, or 30 nm to 50 nm shorter under electrical bias than the same LED structures grown on templates containing porous regions.

[0042] For example, the LED light-emitting region can be an LED light-emitting region that emits light at a peak wavelength 15 to 80 nm lower than the desired peak emission wavelength of the LED, and the porous region of the group III nitride material can redshift the emission spectrum of the light-emitting region by 15 to 80 nm to reach the peak emission wavelength of the LED according to the present invention.

[0043] Alternatively, the LED light-emitting region can be an LED light-emitting region that emits light at a peak wavelength 15 nm to 50 nm lower than the desired peak emission wavelength of the LED, and the porous region of the group III nitride material can redshift the emission spectrum of the light-emitting region by 15 nm to 50 nm to reach the peak emission wavelength of the LED according to the present invention.

[0044] Alternatively, the LED light-emitting region can be an LED light-emitting region that emits light at a peak wavelength 30 nm to 50 nm, or preferably 30 nm to 40 nm lower than the desired peak emission wavelength of the LED, and the porous region of the group III nitride material can redshift the emission spectrum of the light-emitting region by 30 nm to 50 nm or 30 nm to 40 nm to reach the peak emission wavelength of the LED according to the present invention.

[0045] The LED light-emitting region is an LED light-emitting region that, when grown on a non-porous GaN template, is suitable for or configured to emit light at various different peak wavelengths. For example, the LED light-emitting region is an LED light-emitting region configured to emit blue light (e.g., 475 nm), which is known in the art, when grown on a conventional non-porous semiconductor template. However, by growing this "blue" LED light-emitting region on a porous template to form an LED according to the present invention, the LED structure undergoes a redshift, and the LED begins to emit light at wavelengths longer than the normal 475 nm emission wavelength.

[0046] For example, if an LED light-emitting region is not grown on a porous III nitride layer, it will emit light at peak wavelengths of 520-555 nm, 445-520 nm, 400-445 nm, or 385-425 nm. However, by growing an LED light-emitting region on a porous region of a Group III nitride material, the emission wavelength of the light-emitting region can be shifted to a peak emission wavelength longer than the expected peak wavelength of that light-emitting region.

[0047] Previous attempts to incorporate porous materials into LEDs have shown that the porous material causes a high degree of spectral broadening, resulting in an unnecessarily wide full width at half maximum (FWHM) of the spectral emission peak. This is undesirable in most LED applications, as a narrow emission peak is preferable for the light emitted by the LED to be at or near the desired wavelength.

[0048] Advantageously, the LED in the present invention preferably emits light with an FWHM of 50 nm or less, or 40 nm or less, or 30 nm or less, preferably with an FWHM of less than 40 nm, and more preferably less than 20 nm.

[0049] In a preferred embodiment, the light-emitting layer is an indium gallium nitride light-emitting layer. The LED preferably also includes a region of GaN material. Due to the lattice mismatch between GaN and InGaN, the stress relaxation effect generated by the porous region is particularly advantageous.

[0050] The light-emitting diode has at least one feature selected from the following: (a) The light-emitting region includes 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 quantum wells (or at least 1 quantum well), (b)III Nitride layer has composition Al y Ga (1-y) It contains an aluminum gallium nitride layer containing N, and y is in the range of 0.1 to 1.0, or (c) The material is provided with an ultraviolet-emitting or blue-emitting InGaN / GaN, an InGaN / InGaN superlattice, or an InGaN layer between the n-doped area and the light-emitting region.

[0051] Orange LED In a preferred embodiment of the present invention, the LED is an orange LED, and the light-emitting region emits light at a peak wavelength of 590-599 nm or 592-597 nm under electrical bias.

[0052] To provide an orange LED when growing an LED structure on a porous region, the LED light-emitting region can be an LED light-emitting region that emits light at a peak wavelength of 540-560 nm or 540-580 nm, and the porous region of the group III nitride material can shift the emission wavelength of the light-emitting region to a yellow wavelength such as 590-599 nm.

[0053] yellow LED In a preferred embodiment of the present invention, the LED is a yellow LED, and the light-emitting region emits light at a peak wavelength of 570-589 nm or 580-595 nm under electrical bias.

[0054] To provide a yellow LED when growing an LED structure on a porous region, the LED light-emitting region can be an LED light-emitting region that emits light at a peak wavelength of 520-540 nm or 540-560 nm, and the porous region of the group III nitride material shifts the emission wavelength of the light-emitting region to a yellow wavelength such as 570-589 nm or 575-585 nm.

[0055] In one preferred embodiment of a yellow LED, the light-emitting layer is composed of In x Ga 1-x N has a value such that 0.25 ≤ x ≤ 0.35.

[0056] Green LED In another preferred embodiment of the present invention, the LED is a green LED, and the light-emitting region preferably emits light at a peak wavelength of 500-569 nm, 510-555 nm, or 520-540 nm under electrical bias.

[0057] To provide a green LED when growing an LED structure on a porous region, the LED light-emitting region can be an LED light-emitting region that emits light at a peak wavelength of 450-520 nm, and the porous region of the group III nitride material shifts the emission wavelength of the light-emitting region to a green wavelength such as 500-569 nm or 520-540 nm. Alternatively, the LED light-emitting region can be an LED light-emitting region that emits light at a peak wavelength of 470-540 nm, and the porous region of the group III nitride material shifts the emission wavelength of the light-emitting region to a longer green wavelength.

[0058] In one preferred embodiment of a green LED, the light-emitting layer is composed of In x Ga 1-x N has a value such that 0.22 ≤ x ≤ 0.30, and preferably x = 0.25.

[0059] Blue LED In another preferred embodiment of the present invention, the LED is a blue LED, and the light-emitting region emits light at a peak wavelength of 450-499 nm, 450-485 nm, or 460-475 nm under electrical bias.

[0060] To provide a blue LED when growing an LED structure on a porous region, the LED light-emitting region can be an LED light-emitting region that emits light at a peak wavelength of 400-450 nm or 420-430 nm, and the porous region of the group III nitride material shifts the emission wavelength of the light-emitting region to a blue wavelength such as 450-499 nm. Alternatively, the LED light-emitting region can be an LED light-emitting region that emits light at a peak wavelength of 420-470 nm, and the porous region of the group III nitride material shifts the emission wavelength of the light-emitting region to a longer blue wavelength such as 450-499 nm.

[0061] In one preferred embodiment of the cyan LED, the light-emitting layer has the composition In x Ga 1-x N, where 0.12 ≦ x ≦ 0.25, or 0.15 ≦ x ≦ 0.22.

[0062] purple LED In another preferred aspect of the present invention, the LED is a violet LED, and the light-emitting region emits light at a peak wavelength of 400 - 449 nm or 410 - 430 nm under an electrical bias.

[0063] To provide a violet LED when growing an LED structure on a porous region, the LED light-emitting region can preferably be an LED light-emitting region that emits light at a peak wavelength of 385 - 425 nm, and the porous region of the group III nitride material shifts the emission wavelength of the light-emitting region to 400 - 449 nm.

[0064] In one preferred embodiment of the violet LED, the light-emitting layer has the composition In x Ga 1-x N, where 0.05 ≦ x ≦ 0.17, or 0.07 ≦ x ≦ 0.12.

[0065] template The n-type region, the light-emitting region, and the p-type region (which can be referred to as the LED structure) are preferably grown on a semiconductor template including a porous region. The semiconductor template also includes a number of semiconductor material layers arranged to provide a substrate suitable for the growth of the LED structure. However, once the n-type region, the light-emitting region, and the p-type region are grown on the template, both the LED structure and the template form part of the LED.

[0066] The porous region has a thickness of at least 1 nm, preferably at least 10 nm, and particularly preferably at least 50 nm. For example, the porous region has a thickness of 1 nm - 10000 nm.

[0067] Porous regions can have porosity levels of 1% to 99%, 10% to 80%, 20% to 70%, or 30% to 60%. The porosity of a porous region is measured as the volume of all pores relative to the total volume of the porous region.

[0068] It has been revealed that porosity affects the magnitude of the wavelength shift caused by porous regions. Generally, higher porosity results in a larger wavelength shift of the LED compared to the same LED structure formed on a non-porous template.

[0069] The porous region is preferably formed from one of GaN, InGaN, AlGaN, AlInGaN, or AlN.

[0070] The porous region can be located directly below or below the n-type region, the light-emitting region, and the p-type region. Preferably, the n-type region, the light-emitting region, and the p-type region (LED structure) are positioned above or above the porous region, as defined by the layer growth sequence within the LED. Since the LED structure is preferably grown on the porous region, the LED structure benefits from the strain relaxation of the porous group III nitride layer.

[0071] The LED includes a connecting layer of III nitride material positioned between the n-doped region and the porous region. Preferably, the thickness of the connecting layer is at least 100 nm, but a smaller or larger thickness may be used. The connecting layer can preferably be one of GaN, InGaN, AlGaN, AlInGaN, or AlN.

[0072] The LED preferably includes a non-porous intermediate layer of a Group III nitride material between the porous region and the light-emitting region. The porous region is preferably formed by electrochemical porosification through the non-porous layer of the Group III nitride material using the methods of PCT / GB2017 / 052895 (published as WO2019 / 063957) and PCT / GB2019 / 050213 (published as WO2019 / 145728). Thus, the non-porous layer of the Group III nitride material usually forms a non-porous intermediate layer that is maintained on top of the porous region. The non-porous intermediate layer advantageously provides a smooth surface for further layer growth during manufacturing.

[0073] Preferably, the LED includes a non-porous intermediate layer of a group III nitride material positioned between the porous region and the connecting layer. Preferably, electrochemical etching of the porous region is performed through the non-porous layer.

[0074] The non-porous intermediate layer can preferably be one of GaN, InGaN, AlGaN, AlInGaN, or AlN.

[0075] The porous region can be a single porous layer, and therefore the light-emitting diode includes a porous layer of group III nitride material. Preferably, the porous region is a continuously porous layer formed from, for example, a continuous layer of porous group III nitride material.

[0076] The porous region may include multiple porous layers and optionally multiple non-porous layers. In a preferred embodiment of the present invention, the porous region is a stack of alternating porous and non-porous layers, where the upper surface of the stack defines the upper part of the porous region and the lower surface of the stack defines the lower part of the porous region. The light-emitting region is formed on top of the porous region, which includes a stack of porous layers of a group III nitride material.

[0077] In some embodiments, the light-emitting region is positioned on a stack of multiple porous layers of a group III nitride material. Therefore, the porous region is not a single porous layer of group III nitride material, but rather a stack of multiple layers of group III nitride material, each having at least some porous layers. Preferably, the stack of porous layers consists of alternating layers of porous and non-porous layers.

[0078] Alternatively, a porous region is a layer of Group III nitride material containing one or more porous regions; for example, one or more porous regions are contained within a non-porous layer of Group III nitride material. In other words, a porous region does not need to be a continuous layer of porous material.

[0079] In a preferred embodiment, the porous region or porous layer has lateral dimensions (width or length) equivalent to those of the substrate on which the porous layer or porous region is grown. For example, conventional substrate wafer sizes can vary, for example, 1 cm 2 These are 2 inches, 4 inches, 6 inches, 8 inches, 12 inches, or 16 inches in diameter. However, by patterning one or more layers and / or depositing regions with different charge carrier concentrations within the same layer, it is also possible to form small porous regions that do not extend to the entire substrate. Therefore, the lateral dimensions of the porous layer or porous region vary from about one-tenth the size of a pixel (e.g., 0.1 μm) to the lateral dimensions of the substrate itself.

[0080] The n-doped portion preferably includes an n-doped group III nitride layer.

[0081] Preferably, the n-doped portion and / or n-doped layer includes a stack consisting of alternating layers of n-GaN, n-InGaN, or n-GaN / n-InGaN layers, or a stack consisting of alternating layers of n-InGaN / n-InGaN layers containing different concentrations of indium.

[0082] The n-doped portion may include a single-crystal n-doped group III nitride portion. Preferably, the n-doped portion includes a single-crystal n-doped group III nitride layer having a flat top surface.

[0083] Each of the porous regions, and each of the layers between the porous region and the single-crystal n-doped group III nitride layer, can be a flat layer having an upper surface and a lower surface parallel to the flat upper surface of the single-crystal n-doped group III nitride layer.

[0084] The light-emitting layer preferably includes one or more InGaN quantum wells, and more preferably includes 1 to 7 quantum wells.

[0085] The light-emitting layer can be an InGaN nanostructure layer containing quantum structures such as quantum dots, fragmentary quantum wells, or discontinuous quantum wells.

[0086] The light-emitting layer and / or quantum well is preferably composed of In x Ga 1-x N has a coefficient of 0.07 ≤ x ≤ 0.35, preferably 0.12 ≤ x ≤ 0.30 or 0.22 ≤ x ≤ 0.30, and particularly preferably 0.22 ≤ x ≤ 0.27.

[0087] The LED preferably includes a group III nitride layer disposed on a light-emitting layer and a group III nitride barrier layer disposed on the group III nitride layer.

[0088] The group III nitride layer on the emissive layer is called the "cap layer." This cap layer is used to 1) increase the quantum confinement Stark effect for band bending, thereby achieving redshift and long-wavelength emission, and 2) protect the high In% within InGaN, ensuring sufficient In% incorporation to achieve long wavelengths and provide a large barrier.

[0089] The LED preferably includes a cap layer of a group III nitride material between the quantum well and the p-doped region. The cap layer may be GaN, InGaN, AlGaN, or AlN.

[0090] The LED preferably includes a barrier layer of a group III nitride material between the quantum well and the p-doped region. The barrier layer may be GaN, InGaN, AlGaN, or AlN.

[0091] The p-doped region includes a p-doped group III nitride layer and a p-doped aluminum gallium nitride layer positioned between the p-doped group III nitride layer and the light-emitting region. The p-doped aluminum nitride layer is preferably an electron blocking layer (EBL) positioned between the cap layer and the p-type layer, and the electron blocking layer contains 5 to 25 at% aluminum, and preferably the thickness of the electron blocking layer is 10 to 50 nm.

[0092] The porous region is preferably not part of the distributed Bragg reflector (DBR).

[0093] Pixel size The light-emitting region and / or LED has lateral dimensions (width and length) greater than 100 μm and less than 300 μm. In this case, the LED can be called a "mini-LED". In a preferred embodiment, the mini-LED can be rectangular, circular, or rectangular with rounded corners, and has dimensions such as 300 μm × 300 μm, 200 μm × 200 μm, 100 μm × 100 μm, etc.

[0094] Alternatively, the light-emitting region and / or LED has lateral dimensions (width and length) of less than 100 μm. In this case, the LED can be called a "micro-LED". Micro-LEDs preferably have lateral dimensions of less than 80 μm, or less than 70 μm, or less than 60 μm, or less than 50 μm, or less than 30 μm, or less than 25 μm, or less than 20 μm, or less than 15 μm, or less than 10 μm, or less than 5 μm, or less than 3 μm, or less than 1 μm, or less than 500 nm, or less than 200 nm, or less than 100 nm, or less than 50 nm.

[0095] In a preferred embodiment, the microLED can be rectangular or circular or rectangular with rounded corners, and have dimensions of 75 μm × 75 μm, 50 μm × 50 μm, 40 μm × 40 μm, 30 μm × 30 μm, 25 μm × 25 μm, 20 μm × 20 μm, or 10 μm × 10 μm, or 5 μm × 5 μm, or 2 μm × 2 μm, or 1 μm × 1 μm, or 500 nm × 500 nm, or smaller.

[0096] LEDs can be arbitrarily circular, square, rectangular, hexagonal, or triangular in shape. In the case of irregularly shaped pixel designs, at least one dimension must fall within the dimensions specified above to classify the LED as a mini-LED or micro-LED. For example, to classify an LED as a micro-LED, the width or diameter of the LED is preferably less than 100 μm.

[0097] Mini LED In a second aspect of the present invention, a mini-LED including an LED according to the first aspect of the present invention can be provided. In this mini-LED, the light-emitting area has lateral dimensions (width and length) greater than 100 μm and less than 300 μm or 200 μm. In a preferred embodiment, the mini-LED can be rectangular, circular, or rectangular with rounded corners, and has dimensions such as 300 μm × 300 μm, 200 μm × 200 μm, or 100 μm × 100 μm.

[0098] Micro LED In a third aspect of the present invention, a micro-LED including an LED according to the first aspect of the present invention can be provided. In this micro-LED, the light-emitting region has a lateral dimension less than 100 μm. Preferably, the micro-LED has a lateral dimension of less than 80 μm, or less than 70 μm, or less than 60 μm, or less than 50 μm, or less than 30 μm, or less than 25 μm, or less than 20 μm, or less than 15 μm, or less than 10 μm, or less than 5 μm, or less than 3 μm, or less than 1 μm, or less than 500 nm, or less than 200 nm, or less than 100 nm, or less than 50 nm.

[0099] Micro LED array In a fourth aspect of the present invention, an array of micro-LEDs including a plurality of micro-LEDs according to a third aspect of the present invention can be provided.

[0100] Green LED According to a fifth aspect of the present invention, a green light-emitting diode (LED) is provided. This green LED is n-doped section and, p-doped section, It includes an luminescent region positioned between the n-doped and p-doped regions, and the luminescent region is A light-emitting layer that emits light at a peak wavelength of 500-570 nm under electrical bias, It includes a group III nitride layer disposed on a light-emitting layer and a group III nitride barrier layer disposed on the group III nitride layer, LEDs include porous regions in Group III nitride materials.

[0101] The light-emitting region of the green LED preferably emits light at a peak wavelength of 500-570 nm, 510-555 nm, or 520-540 nm under electrical bias.

[0102] To provide a green LED when growing an LED structure on a porous region, the LED light-emitting region can be an LED light-emitting region that emits light at a peak wavelength of 450-520 nm or 470-510 nm, and the porous region of the group III nitride material can shift the emission wavelength of the light-emitting region to a green wavelength such as 500-570 nm or 520-540 nm.

[0103] In one preferred embodiment of a green LED, the light-emitting layer is composed of In x Ga 1-x N has a value such that 0.22 ≤ x ≤ 0.30, and preferably x = 0.25.

[0104] The characteristics described above in relation to the first to fourth embodiments also apply equally to green LEDs.

[0105] Blue LED According to a sixth aspect of the present invention, a blue light-emitting diode (LED) is provided. This blue LED is n-doped section and, p-doped section, It includes an luminescent region positioned between the n-doped and p-doped regions, and the luminescent region is A light-emitting layer that emits light at a peak wavelength of 450-500 nm under electrical bias, It includes a group III nitride layer disposed on a light-emitting layer and a group III nitride barrier layer disposed on the group III nitride layer, LEDs include porous regions in Group III nitride materials.

[0106] The emission region emits light at peak wavelengths of 450-500 nm, 455-485 nm, or 460-475 nm under electrical bias.

[0107] To provide a blue LED when growing an LED structure on a porous region, the LED light-emitting region can be an LED light-emitting region that emits light at a peak wavelength of 400-445 nm or 420-430 nm, and the porous region of the group III nitride material shifts the emission wavelength of the light-emitting region to a blue wavelength such as 450-500 nm.

[0108] In one preferred embodiment of a blue LED, the light-emitting layer is composed of In x Ga 1-x Let N be such that 0.12 ≤ x ≤ 0.22 or 0.15 ≤ x ≤ 0.20.

[0109] The characteristics described above in relation to the first to fourth embodiments also apply equally to blue LEDs.

[0110] Manufacturing method A seventh aspect of the present invention provides a method for manufacturing an LED, which is: n-doped section and, p-doped section, A light-emitting region positioned between an n-doped region and a p-doped region, comprising a light-emitting layer that emits light at a peak wavelength of 400-599 nm under electrical bias, The process includes growing an LED containing on a porous region of a group III nitride material.

[0111] Alternatively, the method involves growing an LED structure on a porous region of a group III nitride material at a growth temperature higher than previously possible. The presence of a porous region in the group III nitride material means that the semiconductor lattice is relaxed, allowing for the indium necessary for growing the InGaN light-emitting layer to be incorporated using a higher-than-usual growth temperature. While the LED structure grown on the porous region is a known LED structure, in this case, using a porous template makes it possible to grow an LED light-emitting layer, such as an InGaN quantum well (QW), at a higher growth temperature than possible when growing on a non-porous substrate.

[0112] In an eighth aspect of the present invention, a method for manufacturing an LED can be provided, and this method is n-doped section and, p-doped section, A light-emitting region positioned between an n-doped region and a p-doped region, comprising a light-emitting layer that emits light at a peak wavelength of 385 to 555 nm under electrical bias, The process includes growing an LED containing on a porous region of a group III nitride material, wherein growth on the porous region of the group III nitride material shifts the emission wavelength of the emission region to a peak wavelength of 400-599 nm under electrical bias.

[0113] According to a ninth aspect of the present invention, a method for manufacturing an LED having a peak emission wavelength of 400 nm to 599 nm under electrical bias can be provided. This method is n-doped section and, p-doped section, An emission region for emitting light at a peak wavelength lower than the peak emission wavelength of the LED, The process includes the step of growing an LED structure containing on a porous region of a group III nitride material, wherein the porous region of the group III nitride material causes the emission wavelength of the emission region to redshift to the peak emission wavelength.

[0114] An LED structure including n-doped areas, p-doped areas, and light-emitting regions can be configured to emit light at a wavelength lower than the peak emission wavelength of the LED, and the porous region of the group III nitride material causes the emission wavelength of the light-emitting region to redshift to the peak emission wavelength.

[0115] The following considerations apply to the methods of the seventh, eighth, and ninth aspects of the present invention.

[0116] The LED light-emitting region can be configured to emit light at a peak wavelength 15-80 nm lower than the desired peak emission wavelength of the LED, and the porous region of the group III nitride material can cause the emission spectrum of the light-emitting region to be redshifted by 15-80 nm.

[0117] Alternatively, the LED light-emitting region can be configured to emit light at a peak wavelength 15 nm to 50 nm lower than the desired peak emission wavelength of the LED, and the porous region of the group III nitride material can cause the emission spectrum of the light-emitting region to be redshifted by 15 nm to 50 nm.

[0118] The LED light-emitting region can be configured to emit light at various different peak wavelengths when grown on a non-porous GaN template. For example, the LED light-emitting region, when grown on a conventional non-porous semiconductor template, is configured to emit blue light (e.g., 475 nm), which is known in the art. However, by growing this "blue" LED light-emitting region on a porous template to form an LED according to the present invention, the LED structure undergoes a redshift, and the LED begins to emit light at wavelengths longer than the normal 475 nm emission wavelength.

[0119] For example, if an LED light-emitting region is not grown on a porous III nitride layer, it will emit light at peak wavelengths of 520-555 nm, 445-520 nm, 400-445 nm, or 385-425 nm. However, by growing the LED light-emitting region on a porous region of a group III nitride material, the emission wavelength of the light-emitting region can be shifted to a peak emission wavelength longer than the expected peak wavelength of that light-emitting region.

[0120] In a preferred embodiment, the light-emitting layer is a light-emitting indium gallium nitride layer. The LED preferably also includes a region of GaN material. Due to the lattice mismatch between GaN and InGaN, the stress relaxation effect generated by the porous region is particularly advantageous.

[0121] Manufacturing of orange LEDs This method can be used to manufacture an orange LED having a peak emission wavelength of 590 nm to 599 nm under electrical bias.

[0122] To provide a yellow LED when growing an LED structure on a porous region, the LED light-emitting region can be an LED light-emitting region that emits light at a peak wavelength of 540-560 nm, while the porous region of the group III nitride material shifts the emission wavelength of the light-emitting region to an orange wavelength, such as 590-599 nm.

[0123] In one preferred embodiment of an orange LED, the light-emitting layer is composed of In x Ga 1-x N has a value such that 0.25 ≤ x ≤ 0.35.

[0124] Manufacturing of yellow LEDs This method can be used to manufacture a yellow LED having a peak emission wavelength of 570nm to 589nm or 575 to 585nm under electrical bias.

[0125] To provide a yellow LED when growing an LED structure on a porous region, the LED light-emitting region can be an LED light-emitting region that emits light at a peak wavelength of 520-540 nm or 540-560 nm, and the porous region of the group III nitride material shifts the emission wavelength of the light-emitting region to a yellow wavelength such as 570-589 nm or 575-585 nm.

[0126] In one preferred embodiment of a yellow LED, the light-emitting layer is composed of In x Ga 1-x N has a value such that 0.25 ≤ x ≤ 0.35.

[0127] Manufacturing of green LEDs This method can be used to manufacture a green LED having a peak emission wavelength of 500nm-570nm, 510-555nm, or 520-540nm under electrical bias.

[0128] To provide a green LED when growing an LED structure on a porous region, the LED light-emitting region is an LED light-emitting region that emits light at a peak wavelength of 450-520 nm or 470-540 nm, and the porous region of the group III nitride material shifts the emission wavelength of the light-emitting region to a green wavelength such as 495-570 nm or 520-540 nm, or a longer green wavelength.

[0129] In one preferred embodiment of a green LED, the light-emitting layer is composed of In x Ga 1-x N has a value such that 0.22 ≤ x ≤ 0.30, and preferably x = 0.25.

[0130] Manufacturing of blue LEDs The method can be a method for manufacturing a blue LED having a peak emission wavelength of 450 nm to 499 nm, 450 to 485 nm, or 460 to 475 nm under electrical bias.

[0131] To provide a blue LED when growing an LED structure on a porous region, the LED light-emitting region can be an LED light-emitting region that emits light at a peak wavelength of 400-450 nm or 420-470 nm, and the porous region of the group III nitride material can shift the emission wavelength of the light-emitting region to a blue wavelength such as 450-499 nm, or a longer blue wavelength.

[0132] In one preferred embodiment of a blue LED, the light-emitting layer is composed of In x Ga 1-x N has a value such that 0.12 ≤ x ≤ 0.22 or 0.15 ≤ x ≤ 0.20.

[0133] Manufacturing of purple LEDs This method can be used to manufacture a blue LED having a peak emission wavelength of 400-449 nm or 410-430 nm under electrical bias.

[0134] To provide a purple LED when growing an LED structure on a porous region, the LED light-emitting region can be an LED light-emitting region that emits light at a peak wavelength of 385-425 nm, while the porous region of the group III nitride material shifts the emission wavelength of the light-emitting region to 400-449 nm.

[0135] In one preferred embodiment of a purple LED, the light-emitting layer is composed of In x Ga 1-x N has a value such that 0.05 ≤ x ≤ 0.17 or 0.07 ≤ x ≤ 0.12.

[0136] Manufacturing steps The n-type region, the light-emitting region, and the p-type region (which can be called the LED structure) are preferably grown on a semiconductor template that includes a porous region. The semiconductor template may also include a number of semiconductor layers arranged to provide a substrate suitable for growing the LED structure.

[0137] The method includes a first step of electrochemically porousizing a group III nitride material layer to form porous regions of the group III nitride material. This is achieved using a wafer-scale porosification process described in international patent applications PCT / GB2017 / 052895 (published as WO2019 / 063957) and PCT / GB2019 / 050213 (published as WO2019 / 145728).

[0138] The method preferably includes the step of forming a porous region of a group III nitride material by electrochemical porosification through a non-porous layer of the group III nitride material, thereby making the non-porous layer of the group III nitride material a non-porous intermediate layer. The non-porous intermediate layer advantageously provides a smooth surface for the growth of further layers, such as one or more connecting layers of the group III nitride material.

[0139] Porous regions are formed by porousizing one or more layers or regions of a group III nitride material on a substrate. Substrates include silicon, sapphire, SiC, and β-Ga2O3. The crystal orientation of the substrate is polar, semipolar, or nonpolar. The substrate thickness typically varies between 100 μm and 1500 μm.

[0140] The porous region can be a single porous layer, and therefore the method includes the steps of growing n-doped areas, p-doped areas, and LED light-emitting areas on a porous layer of a group III nitride material. Preferably, the porous region is a continuously porous layer formed from, for example, a continuous layer of porous group III nitride material.

[0141] The porous region may include multiple porous layers and optionally multiple non-porous layers. In a preferred embodiment of the present invention, the porous region is a stack consisting of alternating layers of porous and non-porous layers, where the top surface of the stack defines the upper part of the porous region and the bottom surface of the stack defines the lower part of the porous region.

[0142] Alternatively, the porous region is a group III nitride material layer containing one or more porous regions, for example, one or more porous regions are contained within a non-porous layer of group III nitride material.

[0143] In a preferred embodiment, the porous region or porous layer has lateral dimensions (width or length) equivalent to those of the substrate on which the porous layer or porous region is grown. For example, conventional substrate wafer sizes can vary, for example, 1 cm 2 These are 2 inches, 4 inches, 6 inches, 8 inches, 12 inches, or 16 inches in diameter. However, by patterning one or more layers and / or depositing regions with different charge carrier concentrations within the same layer, it is possible to form small porous regions that do not extend to the entire substrate. Therefore, the lateral dimensions of the porous layer or porous region vary from about one-tenth the size of a pixel (e.g., 0.1 μm) to the lateral dimensions of the substrate itself.

[0144] Prior to the porous formation step, a doped region of n-doped group III nitride semiconductor material can be deposited on the substrate, preferably comprising a stack of one or more layers. The one or more group III nitride layers contain one or more combinations of the elements Al, Ga, and In (quaternary layer, ternary layer). The thickness of the group III nitride stack is preferably 10 to 4000 nm. The group III nitride region is 1 × 10⁻⁶ 17 cm -3 ~5×10 20 cm -3 It has a doping concentration of [value missing].

[0145] Preferably, an intermediate layer of undoped group III nitride material is deposited on the doped material before the doped material is porous. The thickness of the intermediate layer is preferably 1 nm to 3000 nm, and preferably 5 nm to 2000 nm. Since the intermediate layer is undoped, it remains non-porous after the porousization step, which provides a good surface for the epitaxial growth of further layers of the semiconductor.

[0146] In a preferred embodiment, the doped region is a stack consisting of alternating layers of doped and undoped layers. In a preferred embodiment, the stack includes 5 to 50 pairs of layers. The thickness of each highly doped layer varies between 10 nm and 200 nm, and the thickness of the less doped or undoped layers can be between 5 and 180 nm.

[0147] As is known in this art, electrochemical porosity removes material from the n-type doped region of a group III nitride material, creating empty pores in the semiconductor material.

[0148] In a preferred embodiment, an LED structure is formed on a stack of multiple porous layers of a group III nitride material. Therefore, the porous region is not a single porous layer of the group III nitride material, but rather a stack of multiple layers of the group III nitride material, each having at least some porous layers. The stack of porous layers is preferably composed of alternating layers of porous and non-porous layers.

[0149] The method preferably includes the step of depositing one or more connecting layers of group III nitride material on the surface of an intermediate layer of group III nitride material. After this step, n-doped regions, LED light-emitting regions, and p-doped regions are grown on the connecting layers.

[0150] Alternatively, if there is no non-porous intermediate layer above the porous region, the method includes the step of depositing a connecting layer of group III nitride material on the surface of the porous region of the group III nitride material.

[0151] The method may include further steps of growing n-doped regions, LED light-emitting regions, and p-doped regions on the connecting layer.

[0152] The LED produced by this manufacturing method is preferably an LED according to one of the first to sixth embodiments of the present invention.

[0153] Features described in relation to one aspect of the present invention are equally applicable to other aspects of the present invention. [Brief explanation of the drawing]

[0154] Embodiments of the present invention will now be described with reference to the drawings.

[0155] Figure 1 shows a porous template suitable for LEDs according to the present invention. Figures 2 to 18 show the steps for manufacturing an LED according to a preferred embodiment of the present invention. Figure 19 is a graph showing the normalized electroluminescence (EL) intensity versus wavelength for an InGaN LED on a porous substrate. Figure 20 is a graph showing the normalized electroluminescence (EL) intensity versus wavelength for InGaN LEDs on a non-porous substrate under different current injection conditions. Figure 21 is a graph showing the normalized electroluminescence (EL) intensity versus wavelength for an InGaN LED grown on a porous region, similar to the one in Figure 15, under different current injection conditions. Figure 22 shows the IV curves measured for InGaN microLEDs of various pixel sizes on a non-porous substrate, with the inset plot showing yellow emission. Figure 23 shows the IV curves measured for InGaN microLEDs of various pixel sizes on a porous substrate, with the inset plot showing red light emission. Figure 24A is a graph showing the intensity versus EL wavelength for three types of LEDs grown on different templates. Figure 24B is a graph showing the intensity versus EL wavelength for three types of LEDs grown on different templates. Figure 24C is a graph showing the intensity versus EL wavelength for two types of LEDs grown on different templates. [Modes for carrying out the invention]

[0156] Figure 1 shows a porous template suitable for LEDs according to the present invention.

[0157] The porous template includes a porous region of Group III nitride material on a substrate, with a non-porous layer of Group III nitride material positioned on top of the porous region. Optionally, a further layer of Group III nitride material may also be present between the substrate and the porous region.

[0158] As detailed below, the porous region is provided by epitaxially growing an n-doped region of a group III nitride material, followed by an undoped layer of the group III nitride material, and then porousizing the n-doped region using a porousization process. The porousization process is described in international patent applications PCT / GB2017 / 052895 (published as WO2019 / 063957) and PCT / GB2019 / 050213 (published as WO2019 / 145728).

[0159] As described above, this porosity leads to strain relaxation in the crystal lattice, which means that subsequent growth of semiconductor layers will benefit from reduced compressive strain within the lattice.

[0160] The porous region may include one or more layers made of one or more group III nitride materials and may have a range of thicknesses, but in all cases, the benefit of strain relaxation is obtained by shifting the wavelength of the InGaN emitting layer grown above the porous region. In a preferred embodiment, the porous region includes, for example, GaN and / or InGaN.

[0161] Various LED structures can be grown on the template shown in Figure 1.

[0162] In particular, LED structures containing an InGaN light-emitting layer, which is known in the art for manufacturing yellow or green LEDs, can be grown on a porous template using standard LED manufacturing steps. However, when grown on a porous template, LED structures that normally emit light at a first wavelength will emit light at a longer wavelength due to redshift.

[0163] Thus, by using a porous region of a group III nitride material as a template or pseudo-substrate for growing known InGaN LED structures, LEDs with longer wavelengths can be easily manufactured.

[0164] In a preferred embodiment, an LED according to the present invention comprises the following layers and is manufactured using the stepwise process described below.

[0165] The following description of the LED structure relates to a top-emission architecture, described from bottom to top; however, the present invention is equally applicable to a bottom-emission architecture.

[0166] Figure 2. Substrate and Group III nitride layer for porous structure A compatible substrate is used as the starting surface for epitaxial growth. The substrate may be silicon, sapphire, SiC, β-Ga2O3, GaN, glass, or metal. The substrate crystal orientation can be polar, semipolar, or nonpolar. The substrate size is 1 cm². 2 The diameter can vary from 2 inches, 4 inches, 6 inches, 8 inches, 12 inches, 16 inches, and beyond. The substrate thickness is greater than 1 μm, for example, from 1 μm to 15,000 μm.

[0167] One or more layers of Group III nitride material are epitaxially grown on a substrate. The Group III nitride layer contains one or more combinations of the elements Al, Ga, and In (binary, ternary, or quaternary layers).

[0168] The thickness T of the group III nitride stack is preferably at least 10 nm, or at least 50 nm, or at least 100 nm, for example, 10 to 10000 nm.

[0169] Group III nitride layer: 1 × 10 17 cm -3 ~5×10 20 cm -3It includes a doped region having an n-type doping concentration. The group III nitride layer also includes an undoped "cap" layer of group III nitride material above the doped region.

[0170] The doped region terminates on the exposed upper surface of the group III nitride layer, in which case the surface of this layer becomes porous during electrochemical etching.

[0171] Alternatively, the doped region of the group III nitride material may be covered with an undoped "cap" layer of group III nitride material, thereby placing the doped region below the surface of the semiconductor structure. The starting depth (d) of the doped region below the surface can be, for example, 1 to 2000 nm.

[0172] Figure 3 Porousization of the porous region The group III nitride layer (or stack of multiple layers) is deposited on a substrate and then porousd by a wafer-scale porosification process, as described in international patent applications PCT / GB2017 / 052895 (published as WO2019 / 063957) and PCT / GB2019 / 050213 (published as WO2019 / 145728). During this process, the doped regions of the group III nitride material become porous, while the undoped regions of the group III nitride material remain porous.

[0173] After the porousization step, the structure includes porous regions in the locations that were previously n-doped group III nitride material, and optionally also includes a non-porous intermediate layer present on top of these porous regions.

[0174] The porosity of the porous region is controlled by an electrochemical etching process, and may be between 1% and 99%, preferably between 20% and 90% or between 30% and 80%, although lower or higher porosity levels may also be used.

[0175] The thickness of the porous region after porosity formation is preferably greater than 1 nm, more preferably greater than 10 nm, and particularly preferably at least 40 nm, 50 nm, or 100 nm. However, the thickness of the material required to obtain the strain relaxation benefit provided by the porous region varies depending on the type of group III nitride material used to create the porous region.

[0176] The porous region produced by the porousization process is a bulk layer of Group III nitride material having a uniform composition and uniform porosity throughout the entire layer. Alternatively, the porous region comprises multiple porous material layers with different compositions and / or porosity, forming a porous stack of Group III nitride material. For example, the porous region is a continuous layer of porous GaN, or a continuous layer of porous InGaN, or a stack containing one or more layers of porous GaN and / or one or more layers of porous InGaN. The inventors have found that the benefits of strain relaxation of the porous region for growth can be obtained in a wide range of porous regions having stacks of different thicknesses, compositions, and layers.

[0177] In the embodiment shown in the drawing, the porous region is a single porous layer.

[0178] When an undoped cap layer of group III nitride material is present above a doped region, this undoped region remains non-porous even after the surface penetration porosity of the doped region below is performed. The thickness D of this non-porous cap layer is preferably at least 2 nm, or at least 5 nm, or at least 10 nm, and can preferably be 5 to 3000 nm. Providing an undoped cap layer above a doped region has the advantage of obtaining a non-porous layer of group III nitride material that covers the porous region after porosity formation. This non-porous cap layer has the advantage of allowing further material to grow well above the porous region.

[0179] Since the porosity methods described in PCT / GB2017 / 052895 (published as WO2019 / 063957) and PCT / GB2019 / 050213 (published as WO2019 / 145728) can be applied to the entire semiconductor wafer, there is no need for the processing / patterning / treatment of a template for porosity.

[0180] Figure 4 Connecting layer After forming the porous layer, a group III nitride LED epitaxy structure can be grown on the porous template / pseudo-substrate provided by the porous layer and the non-porous cap layer.

[0181] The first layer used to grow the LED structure on the template can be called the connection layer 1.

[0182] While it is possible to grow the LED epitaxial structure directly on the non-porous cap layer, it is preferable to provide a connecting layer 1 on the cap layer before growing the LED structure. The inventors have found that using a group III nitride connecting layer 1 between the porous region and the LED epitaxy structure advantageously ensures a good epitaxial relationship between the LED and the porous template / substrate. The growth of this layer ensures that subsequent growth on the connecting layer is smooth and epitaxial, resulting in appropriately high quality.

[0183] The connecting layer 1 is formed of a group III nitride material and contains one or more combinations of the elements Al, Ga, and In (a binary, ternary, or quaternary layer).

[0184] The connecting layer is either a doped or undoped layer. The connecting layer is optionally doped with a suitable n-type dopant material such as Si, Ge, C, or O. The group III nitride layer is 1 × 10⁻⁶ 17 cm -3 ~5×10 20 cm -3 It has a doping concentration of [value missing].

[0185] The thickness of this connecting layer is preferably at least 100 nm, and can be, for example, 100 to 10000 nm.

[0186] Figure 5 N-doped region After the connecting layer has grown, the bulk n-doped group III nitride region 2 is grown.

[0187] The n-doped region 2 may include or consist of a stack of indium-containing group III nitride layers, or thin group III nitride layers that may or may not contain indium, or it may involve growing a bulk group III nitride layer or a stack of group III nitride layers in which the atomic percentage of indium varies within the bulk layer or stack. For example, the n-doped region may consist of a stack of n-GaN layers, or n-InGaN layers, or alternating layers of n-GaN / n-InGaN layers, or alternating layers of n-InGaN / n-InGaN layers having different amounts of indium.

[0188] Preferably, the n-doped region 2 contains indium, so the crystal lattice of the n-doped region has lattice parameters similar to those of the InGaN light-emitting layer of the LED. The percentage of indium atoms in the n-doped region varies, for example, between 0.1 and 25%.

[0189] In a preferred embodiment, the indium content of the n-doped region is 20 at% or less, or 15 at% or less, or 10 at% or less, or 5 at% or less of the indium content of the InGaN emissive layer. This ensures that the lattice parameters of the n-doped region are sufficiently similar to those of the InGaN emissive layer, advantageously guaranteeing the avoidance of excessive strain between these layers.

[0190] The total thickness of the n-doped region is at least 2 nm, or at least 5 nm, or at least 10 nm, or at least 20 nm. The thickness of the n-doped region may vary, for example, between 2 nm and 5000 nm, or may be thicker. If the n-doped region includes a stack of multiple layers, the thickness of each individual layer in the stack is preferably 1 to 40 nm.

[0191] Preferably, the n-type doping concentration in the n-doped region is 1 × 10⁻⁶ 17 cm -3 ~5×10 20 cm -3 Preferably 1 × 10 18 cm -3 ~5×10 20 cm -3 And, particularly preferably, 1 × 10 18 cm -3 Higher.

[0192] Figure 6. Emitting region After growing n-doped region 2, an underlay, pre-layer, or pre-well (not numbered in Figure 6) can be grown to release strain within one or more emissive layers. The underlay can be a single layer of GaN or InGaN, or a stack / multiple layers of GaN, InGaN, GaN / InGaN, or InGaN / InGaN. Alternatively, the underlay may have a structure similar to an InGaN QW / GaN quantum barrier but with a lower indium content. For example, before depositing an emissive layer with a relatively high indium content, an underlay consisting of a bulk InGaN layer with a lower indium content than the emissive layer can be grown. Alternatively, the underlay can take the form of an InGaN "dummy" QW with a lower indium content than the emissive layer, and one or more GaN quantum barriers.

[0193] After growing the n-doped region 2 and optionally the substrate, an emissive region 3 containing an InGaN emissive layer is grown.

[0194] The light-emitting region 3 includes at least one InGaN light-emitting layer. Each InGaN light-emitting layer can be an InGaN quantum well (QW). Preferably, the light-emitting region includes 1 to 7 quantum wells. Adjacent quantum wells are separated by a barrier layer of a group III nitride material having a different composition from the quantum wells.

[0195] One or more light-emitting layers, which can be referred to as "quantum wells" throughout this document, can take various forms. For example, the light-emitting layer may be a continuous layer of InGaN, or a continuous layer, a fragmented layer, a discontinuous layer, a layer with gaps, or it may be nanostructured to substantially contain multiple 3D nanostructures in which the quantum well behaves as quantum dots.

[0196] Quantum wells and barriers are grown in a temperature range of 600-800°C.

[0197] Each quantum well consists of an InGaN layer having an atomic indium percentage of 15-40%. Preferably, one or more luminescent indium gallium nitride layers and / or quantum wells have an InGaN composition. x Ga 1-x N has 0.05≦x≦0.35, preferably 0.12≦x≦0.30, or 0.22≦x≦0.30, particularly preferably 0.22≦x≦0.27.

[0198] The thickness of each quantum well layer is 1.5 to 8 nm, preferably 1.5 nm to 6 nm, or 1.5 nm to 4 nm. The quantum wells may be covered with a thin (0.5 to 3 nm) group III nitride QW capping layer, which contains one or more combinations of the elements Al, Ga, and In (quaternary layer, ternary layer).

[0199] The QW capping layer, which is added immediately after QW growth, is made of AlN, AlGaN with an Al% of 0.01 to 99.9%, GaN, or InGaN with an In% of 0.01 to 30%.

[0200] The group III nitride QW barrier separating the light-emitting layer (quantum well) contains one or more combinations of the elements Al, Ga, and In (quaternary layer, ternary layer). The QW barrier can be AlN, AlGaN with an Al% of 0.01 to 99.9%, GaN, and InGaN with an In% of 0.01 to 15%. Preferably, the QW barrier layer contains AlN and / or AlGaN.

[0201] Since one or more QW capping layers and QW barriers form part of the light-emitting region 3, these layers are not shown with individual reference numbers in the drawings.

[0202] The QW capping layer is grown after each QW growth and before the barrier growth. For example, if an LED contains three QWs, a QW capping layer is grown on each of these QWs, and then a QW barrier layer is grown, so the light-emitting region will contain such three QW capping layers and three QW barrier layers.

[0203] 1. The cap can be grown under the same conditions as QW. 2. It is possible to grow this cap by raising the temperature to a high level without performing growth (this is essentially an annealing step), and the temperature increase here can be performed in different gas mixtures. 3. Temperature increase and growth during temperature increase can be performed.

[0204] The design of the light-emitting region is modified according to parameters well understood in the art and in conventional LED design. For example, the composition, thickness, and number of layers of the light-emitting and barrier layers are changed depending on the target EL emission wavelength of the LED. As mentioned above in this application, the indium content of the InGaN light-emitting layer is increased when long-wavelength emission is desired.

[0205] As described above, the present invention is provided by growing a known LED structure, known to emit light at a first wavelength under electrical bias, on a template including a porous region. The strain relaxation provided by the porous region beneath the LED structure increases the amount of indium that can be incorporated into one or more light-emitting layers under the same growth conditions, so that the wavelength of the resulting LED is redshifted compared to the same LED structure grown on a non-porous substrate under the same conditions. Therefore, using the present invention, a wider range of emission wavelengths can be achieved than was possible with the prior art. In particular, long wavelengths can be achieved at high InGaN growth temperatures. This provides a crystal structure of superior quality in the LED, and therefore a high-performance LED.

[0206] In the manufacturing of long-wavelength LEDs, the importance of the capping layer becomes even greater because a large amount of indium is present within one or more light-emitting layers. Previous attempts to manufacture long-wavelength yellow, orange, or red LEDs have failed because insufficient indium was incorporated. Therefore, capping is crucial to ensure that sufficient indium is trapped within the light-emitting region.

[0207] Figure 7 Cap layer After the growth of one or more light-emitting layers, an undoped capping layer 4 is grown. The undoped capping layer 4 is formed after the growth of the complete light-emitting region, for example, after the growth of the stack of QW, QW capping layer, and QW barrier layer, and can therefore be called a light-emitting region capping layer.

[0208] The cap layer (light-emitting region cap layer) 4 is a standard layer that is very well known in the growth scheme of Group III nitride LEDs.

[0209] The thickness of the cap layer can be 5 to 30 nm, preferably 5 to 25 nm or 5 to 20 nm.

[0210] The purpose of the luminescence region capping layer 4 is to protect the indium within the luminescence region (QW stack) and prevent this indium from desorbing / evaporating during subsequent processing. This is because, while QWs in InGaN are typically grown at low temperatures, this is undesirable for GaN / AlGaN, and typically a temperature increase step is required before growing further layers above the luminescence region. The capping layer is used to ensure that one or more InGaN luminescence layers are properly capped and protected, and provides an opportunity and time window to change the p-doped layer growth conditions for improved material quality. Additionally, the luminescence region capping layer 4 ensures that Mg dopants do not enter the QW region during the growth of the p-type layer.

[0211] Electron Block Layer (EBL) After growing the quantum well, capping layer, and barrier layer, an aluminum-containing electron block group III nitride (EBL) 5 is grown. The Al% can be, for example, 5-25%, but higher Al content is also possible.

[0212] EBLs are doped with an appropriate p-type doping material. The p-type doping concentration of EBLs is preferably 5 × 10⁻⁶. 18 cm -3 ~8×10 20 cm -3 That is the case.

[0213] The thickness of the EBL is 10 to 50 nm, preferably 20 nm.

[0214] Figure 8 P-doped layer A p-doped layer 6 is grown above the electron block layer (EBL) 5.

[0215] The p-type region is preferably doped with Mg, and the p-type doping concentration in the p-type layer is preferably 5 × 10⁻¹⁰ 18 cm -3 ~8×10 20 cm -3 That is the case.

[0216] The p-doped Group III nitride layer contains In and Ga.

[0217] The doping layer is preferably 20-200 nm thick, and particularly preferably 50-100 nm thick. The doping concentration may vary within the p-type layer, and to enable better p-contacts, the last 10-30 nm portion of this layer, closer to the LED surface, has a spike in the doping level.

[0218] To activate the Mg acceptors in the p-doped layer, the structure can be annealed in an MOCVD reactor or an annealing oven. The annealing temperature is in the range of 700-850°C in an N2 or N2 / O2 atmosphere.

[0219] Since both the EBL and the p-doped layer are p-doped, these layers can be called p-doped regions.

[0220] Figure 9 Transparent conductive layer Next, the stack of active semiconductor layers is covered with a transparent conductive layer 7. The transparent conductive layer is made from Ni / Au, indium tin oxide, indium zinc oxide, graphene, Pd, Rh, silver, ZnO, etc., or a combination of these materials.

[0221] The thickness of the transparent conductive layer is 10 to 250 nm.

[0222] Transparent conductive layers are well known in this field, and any suitable material and thickness can be used.

[0223] In order to make the p-contact ohmic, an annealing step may be necessary.

[0224] Figure 10 Depending on the manufactured LED structure, the semiconductor structure is processed to create an LED, mini-LED, or micro-LED device.

[0225] Conventional LEDs are typically larger than 200 μm (in terms of the lateral dimensions of the LED structure, width and length). Mini LEDs are typically 100-200 μm in lateral size, and micro LEDs are typically smaller than 100 μm.

[0226] Figures 10 onward show the semiconductor structure after etching layers 2-7 of the semiconductor structure to form multiple individual LED stacks or mesas, each having the same structure.

[0227] The steps for manufacturing LEDs are conventional and well known to those skilled in the art. The order of the following manufacturing steps is not unique to the present invention, and it will be acknowledged to those skilled in the art that LED devices within the scope of the present invention can be prepared using alternative manufacturing steps to those described below. However, for illustrative purposes only, one preferred manufacturing method for preparing LEDs according to the present invention is described below.

[0228] In the next step, the transparent conductive layer 7 is structured to cover only the top surface of the active light-emitting element. This structuring can be performed using standard semiconductor processing methods, including resist coating and photolithography. The transparent conductive layer is etched by a wet chemical etching process or a sputter etching process using argon. After this step, wet or dry etching of the group III nitride structure is performed. Mesas are created in the group III nitride layer using inductively coupled plasma reactive ion etching, reactive ion etching alone, or neutral beam etching. The dry etching process may include one or more of the gases Cl, Ar, BCl3, and SiCl4.

[0229] The purpose of this step is to isolate the individual light-emitting elements and to access the embedded n-doped layer of the pn junction.

[0230] After the dry etching process, a wet etching process is performed to remove dry etching damage from the mesa sidewalls. The wet chemicals include KOH (1-20%), TMAH, or other basic chemicals.

[0231] Figure 11 Passivation The next step is to deposit one passivation layer or a combination of multiple passivation layers. The initial passivation layer can be Al2O3 (10-100 nm) (deposited by atomic layer deposition), after which SiO2, SiN, or SiN (50-300 nm) is deposited by sputtering or plasma-excited chemical vapor deposition.

[0232] Al2O3 can be deposited at temperatures between 50 and 150°C.

[0233] SiO2, SiN, and SiN can be deposited at temperatures of 250-350°C.

[0234] The sputtering process can be carried out at room temperature.

[0235] Figures 12 to 13 The next step is to create an opening in the oxide passivation layer 8 to expose the top of the LED structure. This can be done by wet etching, dry etching, or a combination of both.

[0236] For wet etching, buffer oxide etching, diluted hydrofluoric acid, phosphoric acid, or mixtures thereof can be used.

[0237] Furthermore, grooves are etched into the connecting layer 1 between the LED structures, and then dielectric mask material 8 is deposited in the grooves to electrically insulate the LED structures from each other, allowing the LEDs to operate independently of each other.

[0238] The next step in device manufacturing is to cover the transparent conductive layer 7 on the p-doped layer 6 with a metal layer that acts as an electrical p-contact. This covering can be done in a single step or in multiple steps. The metal can completely or partially cover the pixel. In this example, a single step is used for simplicity of explanation.

[0239] The metal may include Ti, Pt, Pd, Rh, Ni, and Au. The thickness of the complete metal stack can be 200 - 2000 nm.

[0240] Figure 14 Exposure of the connecting layer Using standard photolithography techniques, openings are created in the second mask layer 8 to expose multiple regions of the connection layer 1. The size of the openings can vary between 200 nm and 50,000 nm. The distance between the openings is 500 nm - 30,000 nm. The openings are generated only in the regions of the wafer not occupied by the LED structure.

[0241] Preferably, the second mask layer 8 is etched by dry etching using a fluorine-based gas.

[0242] Figure 15 N-contact The next step in device manufacturing is to cover the openings in the oxide 8 with metal contacts 10 to access the connection layer 1 that is in electrical contact with the n-doped layer of the LED structure. Covering in this way can be performed by a single step or multiple steps. The metal covers the pixel completely or partially. In this example, a single step is used to simplify the details.

[0243] The metal includes Ti, Pt, Pd, Rh, Ni, and Au. The thickness of the complete metal stack can be 200 - 2000 nm.

[0244] Figures 16 to 18 After this process, the connection layer 1 is exposed by thinning the substrate and / or removing the porous region.

[0245] Surface structuring or texturing is performed on the substrate, porous region, or layer 1 to increase the light output and control the emission angle as well as other optical engineering and designs. <0​Finally, the wafer / device is flipped over and bonded to a carrier substrate consisting of silicon / sapphire or other types of passive devices. Alternatively, the device is bonded to a CMOS silicon backplane for an active-matrix micro-LED display panel.

[0247] As shown in Figure 16, the upper side of the device is bonded to another carrier wafer / substrate / backplane 11 or to a microdriver circuit board to form an array of pixels.

[0248] As shown in Figure 17, the substrate is removed from the device and the underside of the device is bonded to the cover glass or transparent material 12.

[0249] As shown in Figure 18, the substrate, as well as porous and non-porous regions, are removed from the device. The upper side of the device is bonded to another carrier wafer / substrate / backplane 11 or to a microdriver circuit board to form an array of pixels. The lower side of the device is bonded to a cover glass or transparent material 12.

[0250] Those skilled in the art will understand that the emission wavelength of individual LED structures can be controlled by changing the composition and layer structure of the LED structure according to known principles of LED construction. Therefore, using the present invention, it is possible to provide a variety of tunable wavelength LED devices that emit light in various emission wavelength ranges, and it is also possible to provide color combinations other than green to red.

[0251] Figures 19 to 23 Figure 19 shows an example of an InGaN LED on a porous layer that emits light at a peak wavelength of approximately 625 nm due to a wavelength redshift caused by the porous region.

[0252] Figures 20 and 21 compare the luminescence characteristics of an InGaN LED on a non-porous substrate (Figure 20) and the same InGaN LED grown on a template containing a porous layer of Group III nitride material. Comparing these two graphs demonstrates that the porous underlayer causes a shift to longer emission wavelengths, with the luminescence of the LED on the porous template consistently being 21 nm to 45 nm longer than that of the same LED on a non-porous template.

[0253] Figures 22 and 23 show a comparison of the IV characteristics of a yellow InGaN microLED on a non-porous substrate (Figure 22) and a red InGaN microLED on a template containing a porous layer.

[0254] Figures 24A to 24C The experiments shown in Figures 24A to 24C were performed on a chip-on-wafer (CoW) LED to test the wavelength shift at blue, green, and yellow wavelengths.

[0255] Figures 24A to 24C are graphs of luminous intensity or brightness versus peak EL emission wavelength emitted by an array of chip-on-wafer microLEDs. Figures 24A to 24C were obtained with LEDs configured to emit light at various EL wavelengths between 400 nm and 600 nm, demonstrating that the redshift effect of the present invention can be obtained in a wide range of LEDs with various emission wavelengths.

[0256] Figure 24A shows the results of testing a standard 450nm LED A grown on GaN and flat sapphire substrates (FSS), and it was found that it emitted light mainly in the 440-450nm range under electrical bias. In Figure 24A, the data for LED A is shown as pink data points.

[0257] LED structure LED B, known to emit light at around 420 nm, was grown on a non-porous GaN template. As shown in Figure 19A, LED B emits light at approximately 425–425 nm under electrical bias. In Figure 24A, the data for LED B is shown as dark red data points.

[0258] To demonstrate the wavelength redshift provided by the present invention, LED C, having the same LED structure as LED B, was grown on a template containing a porous GaN region. In Figure 24A, the data for LED C is shown as green data points. LED B (which emits light at a peak wavelength of around 420 nm on a non-porous substrate) was selected as a suitable LED structure for the goal of providing LED C having a peak EL emission wavelength in the range of 430-450 nm, and LED C emits light in the violet region of the visible spectrum when grown on a porous template.

[0259] LED B and LED C have the same LED structure (same active region, as well as the same n-type and p-type regions) and were grown under the same growth conditions using the same epitaxial growth operation. However, as shown in Figure 24A, a significant difference in light emission behavior occurs because LED C is formed on a porous region. Firstly, LED C on porous GaN emits light at longer wavelengths than LED B, i.e., in the range of 430-445 nm compared to 420 nm. Therefore, growth on a porous region resulted in an average wavelength redshift of approximately 10-25 nm in the LEDs within the array. Secondly, by forming LED C on a porous GaN template instead of a non-porous template, the LED light emission intensity was significantly increased as a result of improved quality of the semiconductor layer grown on the strain-relaxed porous region.

[0260] Figure 24B shows that a standard green LED "D" was grown on a non-porous GaN template and found to emit light mainly in the range of 510-530 nm under electrical bias. In Figure 24B, the data for LED D is shown as green data points.

[0261] The same green LED structure was grown on a similar GaN template including a porous GaN layer to form LED E. In FIG. 19B, the data of LED E is shown by the dark red data points. It has been found that LED E emits light at a longer wavelength of an average of 540 - 560 nm compared to the 520 nm emission wavelength of LED D due to a red shift caused by an improvement in the quality of the semiconductor layer grown on the strain-relaxed porous region.

[0262] FIG. 24C shows the comparative data of LED F, which is an LED structure known to emit light at around 540 - 560 nm under an electric bias. In FIG. 24C, the data of LED F is shown by the blue data points.

[0263] To show the wavelength red shift provided by the present invention, LED G having the same LED structure as LED F was grown on a template including a porous GaN region. In FIG. 24C, the data of LED G is shown by the dark red data points. LED F (which emits light at a peak wavelength of around 540 - 560 nm on a non-porous substrate) was selected as an LED structure suitable for the goal of providing LED G having a peak EL emission wavelength within the range of 550 - 570 nm. When grown on a porous template, LED G emits light in the green region of the visible spectrum.

[0264] LED F and LED G have the same LED structure (the same active region, as well as the same n-type region and p-type region) and were grown by the same epitaxial growth operation under the same growth conditions. However, as shown in FIG. 24C, the fact that LED G is formed on a porous region means that LED G on porous GaN emits light at a longer wavelength than LED F, that is, within the range of 550 - 570 nm with respect to 540 - 560 nm. Due to the strain relaxation brought about by the porous region, LED G can incorporate more indium than LED F under the same growth conditions, and as a result, LED G can emit light at a longer wavelength.

Claims

1. Light-emitting diodes (LEDs) n-doped section, p-doped section, It includes a light-emitting region positioned between the n-doped portion and the p-doped portion, The light-emitting region includes a light-emitting layer that emits light at a peak wavelength of 400 to 599 nm under an electrical bias, the light-emitting layer having a composition In x Ga 1-x N with 0.15 ≤ x ≤ 0.35, and includes a group III nitride layer disposed on the light-emitting layer and a group III nitride barrier layer disposed on the group III nitride layer. The light-emitting diode (LED) comprises a porous region of a group III nitride material, a connecting layer of a group III nitride material positioned between the n-doped region and the porous region, and a non-porous intermediate layer of a group III nitride material positioned between the porous region and the connecting layer. The porous region is formed by electrochemical porosity through the non-porous intermediate layer. An LED that emits light with a FWHM of 50 nm or less.

2. The LED according to claim 1, The LED is an orange LED, and the light-emitting region emits light at a peak wavelength of 590-599 nm or 592-597 nm under electrical bias.

3. The LED according to claim 1, The LED is a yellow LED, and the light-emitting region emits light at a peak wavelength of 570-589 nm or 580-585 nm under electrical bias. The aforementioned light-emitting layer has composition In ｘ Ga １－ｘ An LED having a value of N such that 0.25 ≤ x ≤ 0.

35.

4. The LED according to claim 1, The LED is a green LED, and the light-emitting region emits light at a peak wavelength of 500-569 nm, 510-555 nm, or 520-540 nm under electrical bias. The aforementioned light-emitting layer has composition In ｘ Ga １－ｘ An LED having N such that 0.22 ≤ x ≤ 0.30 or x = 0.

25.

5. The LED according to claim 1, The LED is a blue LED, and the light-emitting region emits light at a peak wavelength of 450-499 nm, 460-490 nm, or 470-480 nm under electrical bias. The aforementioned light-emitting layer has composition In ｘ Ga １－ｘ An LED having N such that 0.12 ≤ x ≤ 0.

22.

6. The LED according to claim 1, The LED is a purple LED, and the light-emitting region emits light at a peak wavelength of 400-449 nm, 400-445 nm, or 410-440 nm under electrical bias. The aforementioned light-emitting layer has composition In ｘ Ga １－ｘ An LED having N such that 0.05 ≤ x ≤ 0.

17.

7. The LED according to claim 1, The LED emits light with an FWHM of 40 nm or less, or 30 nm or less, or 20 nm or less, or the LED has an FWHM of 20 to 40 nm.

8. An LED according to claim 1, wherein the light-emitting layer is an indium gallium nitride light-emitting layer.

9. The LED according to claim 8, The indium gallium nitride light-emitting layer has a composition of In ｘ Ga １－ｘ N, and is an LED where 0.20 ≤ x ≤ 0.30 or 0.22 ≤ x ≤ 0.30, or 0.22 ≤ x ≤ 0.

27.

10. The LED according to claim 1, The porous region of the LED has a thickness of at least 1 nm, or at least 10 nm, or at least 50 nm.

11. The LED according to claim 1, The LED has a connecting layer thickness of at least 100 nm, or 100 nm to 1000 nm.

12. The LED according to claim 1, The n-doped portion comprises an n-doped group III nitride layer, or the n-doped portion comprises an LED comprising a stack consisting of alternating layers of n-GaN, n-InGaN, or n-GaN / n-InGaN layers, or an LED comprising an alternating layer of n-InGaN / n-InGaN layers containing different concentrations of indium.

13. A method for manufacturing an LED having a peak emission wavelength of 400 nm to 599 nm under an electrical bias, comprising the step of growing an LED structure on a porous region of a group III nitride material, wherein the LED structure is n-doped section, p-doped section, The device comprises a light-emitting region including a light-emitting layer, the light-emitting layer emits light with a peak emission wavelength of 400 nm to 599 nm under electrical bias, with an FWHM of 50 nm or less, and has a composition of InxGa1-xN, where 0.15 ≤ x ≤ 0.

35. The steps of forming a porous region in a group III nitride material by electrochemical porosity through the non-porous region of the group III nitride material, and the non-porous region of the group III nitride material forming a non-porous intermediate layer, A method for manufacturing an LED, comprising the step of forming one or more connecting layers of group III nitride material on the surface of the non-porous intermediate layer of group III nitride material, and thereafter the step of growing the n-doped portion, the light-emitting region, and the p-doped portion.

14. The method according to claim 13, wherein the light-emitting layer has a composition In ｘ Ga １－ｘ A method for an indium gallium nitride layer having a composition of N such that 0.15 ≤ x ≤ 0.

40.

15. A method according to claim 13, comprising the step of growing the light-emitting region in a temperature range of 600°C to 800°C.

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