Micro LED epitaxial structure of a gradual LQB component and manufacturing method thereof

Abstract

This invention discloses a micro LED epitaxial structure with graded LQB composition, including an InGaN / GaN multi-quantum-well structure, wherein the last quantum well barrier layer on the p-type side of the multi-quantum-well structure is composed of n-type In with graded composition. x Ga 1‑x It consists of an N-type layer and a p-type GaN layer, with the n-type In layer extending from the n-type side to the p-type side. x Ga 1‑x The In composition x of the N-layer gradually changes from 15% to 5% to 0%, and an electron blocking layer is provided on the p-type GaN layer. A graded-change n-type In composition is used. x Ga 1‑x N- and p-type GaN structures, when used as LQB layers in Micro LEDs, can effectively confine charge carriers, resulting in better carrier matching and higher recombination efficiency within the well. This can improve the overall efficiency and luminous level of Micro LED chips under high current density injection, alleviating the problem of efficiency degradation in blue Micro LEDs.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor optoelectronics, and particularly relates to a Micro LED chip epitaxial structure with gradually changed LQB components under high current density and a manufacturing method thereof. BACKGROUND

[0002] Group III nitride visible light LEDs have important applications in the fields of solid-state lighting, optical communication, information storage, etc. Among them, InGaN-based LEDs have a wide range of applications in full-color display and liquid crystal display backlight. Micro light-emitting diode display (Micro LED) as a new generation of display technology, compared with traditional liquid crystal display (LCD) and organic light-emitting diode display (OLED), has the performance advantages of high brightness, high response rate, low power consumption, long service life, etc. These advantages enable it to be applied in AR / VR display, high-resolution display, visible light communication, underwater acoustic communication, etc. and is considered to be the ultimate display technology that is expected to surpass LCD and OLED.

[0003] The existing InGaN-based Micro LED has the problem of efficiency droop, that is, the phenomenon of internal quantum efficiency (IQE) reduction with the increase of current density. The reduction of quantum efficiency has several reasons: insufficient hole injection efficiency, Auger recombination under high carrier density, indirect recombination in the well (Shockley-Read-Hall, SRH recombination) and electron leakage, etc. Therefore, designing a Micro LED epitaxial structure suitable for small size and high current density to limit electron leakage and improve IQE is an important problem that needs to be solved by the industry and academia. SUMMARY

[0004] The application provides a Micro LED chip epitaxial structure with gradually changed LQB components and a manufacturing method thereof to solve the problems in the prior art.

[0005] In order to achieve the above purpose, the technical scheme of the application is as follows:

[0006] A Micro LED epitaxial structure with gradually changed LQB components, comprising an InGaN / GaN multi-quantum well structure, the multi-quantum well structure has an n-type side and a p-type side, wherein the last quantum well barrier layer of the p-type side is composed of an n-type In x Ga 1-x N layer and a p-type GaN layer, and the n-type In x Ga 1-xThe In component x of the N layer gradually changes from 15% to 5% to 0%, and the p-type GaN layer is provided with an electron blocking layer.

[0007] Optionally, the n-type In x Ga 1-x N layer has a thickness of 1-5 nm.

[0008] Optionally, the n-type In x Ga 1-x N layer has an n-doped concentration of 1e17 cm 3 -5e18 cm 3 .

[0009] Optionally, the p-type GaN layer has a p-doped concentration of 1e18 cm 3 -1e20 cm 3 .

[0010] Optionally, the p-type GaN layer has a thickness of 5-20 nm.

[0011] Optionally, the electron blocking layer is a p-type Al y Ga 1-y N layer, where y ranges from 0.10 to 0.25, and the p-doped concentration is 1e19 cm 3 -1e20 cm 3 .

[0012] Optionally, the n-type side is provided with, in order, a substrate, an n-type GaN buffer layer, an electron injection layer, a low-doped n-type GaN layer, and a stress release layer, and the multi-quantum well structure is arranged on the stress release layer.

[0013] Optionally, it further includes a high-temperature p-type GaN layer and a p-electrode contact layer arranged above the electron blocking layer.

[0014] Optionally, the InGaN / GaN multi-quantum well structure includes n-GaN barrier layers and u-In z Ga 1-z N well layers, where z ranges from 0.13 to 0.17; each n-GaN barrier layer has a thickness of 9-12 nm, and each u-In z Ga 1-z N well layer has a thickness of 1-5 nm; the n-type GaN has an n-doped concentration of 1e17 cm 3 -5e18 cm 3 .

[0015] Optionally, the Micro LED epitaxial structure of the gradual LQB component comprises, from bottom to top, a substrate, an n-type GaN layer, an electron injection layer (ESL), a low-doped n-type GaN layer, a plurality of stress release layers (SRLs), a multi-quantum well structure (MQW), a gradually changing last quantum well barrier layer (LQB), an electron blocking layer (EBL), a high-temperature p-type GaN layer, and an electrode contact p-type GaN layer.

[0016] Optionally, the stress release layer comprises an n-GaN barrier layer and a u-In z Ga 1-z N well layer, and z ranges from 0.03 to 0.07.

[0017] Optionally, the thickness of each GaN barrier layer in the stress release layer is 20 nm to 60 nm, and the thickness of each InGaN well layer is 1 nm to 5 nm.

[0018] Optionally, the n-type doping concentration of GaN in the stress release layer is 1e18 cm 3 ~ 5e19 cm 3 .

[0019] Optionally, the electron injection layer is composed of n-Al x Ga 1-x N, and x ranges from 0.05 to 0.15.

[0020] Optionally, the n-type doping concentration of n-Al x Ga 1-x N in the electron injection layer is 1e17 cm 3 ~ 5e18 cm 3 .

[0021] Optionally, the thickness of n-Al x Ga 1-x N in the electron injection layer is 10 nm to 50 nm.

[0022] A preparation method of the above Micro LED epitaxial structure of the gradual LQB component, comprising epitaxial growth of an InGaN / GaN multi-quantum well structure, when growing the last barrier layer, first growing an n-type In x Ga 1-x N layer with In component x gradually changing from 15% to 0% by adjusting the growth temperature, reaction chamber pressure, or source flow, and then growing a p-type GaN layer on the n-type In x Ga 1-x N layer; and growing an electron blocking layer on the p-type GaN layer.

[0023] In the present application:

[0024] x gradually changes n-type Inx Ga 1-x The first part of the N layer as the top quantum barrier, the In composition gradually changes to 0, can be well connected with the subsequent P-GaN layer, without the band mutation, the polarization of the last top quantum barrier is improved to the maximum, the top quantum barrier is in direct contact with the subsequent electron blocking layer, the polarization of the top quantum barrier is improved, the effective potential barrier of the top quantum barrier is improved, and the effective potential barrier of the last electron blocking layer is improved.

[0025] n-type In x Ga 1-x The N layer adopts a very thin thickness, in the case of improving the polarization, the contact surface of the quantum well and the barrier is steep enough to ensure the high quantum efficiency in the well.

[0026] The P-type GaN as the second part of the top quantum barrier, through P-type doping, the effective potential barrier can be further improved. And the P-type doping reduces the height of the valence band barrier, and the P-type doping top barrier layer helps to improve the hole injection.

[0027] The beneficial effects of the present application are:

[0028] The composite quantum barrier top layer structure, the x gradually changing n-type In x Ga 1-x N improves the polarization of the subsequent P-GaN, and the P-type doping of the P-GaN improves the potential barrier of itself, finally, the effective potential barrier height of the top quantum barrier and the electron blocking layer is obviously improved, the electron blocking ability under large current is improved, the electron leakage is effectively reduced, and finally the efficiency decline problem of the Micro LED under high current density (≥1000A·cm -2 ) is improved. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is an epitaxial structure of a low-current Micro LED chip of an embodiment of the present application;

[0030] Figure 2 It is a band diagram of Comparative Example 1 under a current density of 1000A / cm 2 ; and

[0031] Figure 3 It is a band diagram of Example 1 of the present application under a current density of 1000A / cm 2 ; and

[0032] Figure 4 It is a logarithmic electron concentration diagram of Example 1 of the present application and Comparative Example 1 under a current density of 1000A / cm 2 ; and

[0033] Figure 5For Example 1 of the Invention and Comparative Example 1 at 1000 A / cm 2 Hole concentration plot at current density;

[0034] Figure 6 For Example 1 of the Invention and Comparative Example 1 at 1000 A / cm 2 Radiative recombination rate plot at current density;

[0035] Figure 7 For Comparative Example 2 at 1000 A / cm 2 Band diagram at current density;

[0036] Figure 8 For Example 2 of the Invention at 1000 A / cm 2 Band diagram at current density;

[0037] Figure 9 For Example 2 of the Invention and Comparative Example 2 at 1000 A / cm 2 Log electron concentration plot at current density;

[0038] Figure 10 For Example 2 of the Invention and Comparative Example 2 at 1000 A / cm 2 Hole concentration plot at current density;

[0039] Figure 11 For Example 2 of the Invention and Comparative Example 2 at 1000 A / cm 2 Radiative recombination rate plot at current density;

[0040] Figure 12 For Comparative Example 3 at 1000 A / cm 2 Band diagram at current density;

[0041] Figure 13 For Example 3 of the Invention at 1000 A / cm 2 Band diagram at current density;

[0042] Figure 14 For Example 3 of the Invention and Comparative Example 3 at 1000 A / cm 2 Log electron concentration plot at current density;

[0043] Figure 15 For Example 3 of the Invention and Comparative Example 3 at 1000 A / cm 2 Hole concentration plot at current density;

[0044] Figure 16 For Example 3 of the Invention and Comparative Example 3 at 1000 A / cm 2 Radiative recombination rate plot at current density;

[0045] Figure 17 for Comparative Example 4 at 1000 A / cm 2 band diagram at current density;

[0046] Figure 18 for Example 4 of the present application at 1000 A / cm 2 band diagram at current density;

[0047] Figure 19 for Example 4 of the present application and Comparative Example 4 at 1000 A / cm 2 logarithmic electron concentration diagram at current density;

[0048] Figure 20 for Example 4 of the present application and Comparative Example 4 at 1000 A / cm 2 hole concentration diagram at current density;

[0049] Figure 21 for Example 4 of the present application and Comparative Example 4 at 1000 A / cm 2 radiative recombination rate diagram at current density;

[0050] Figure 22 Internal quantum efficiency (IQE) diagrams for Example 1, 2, 3, 4 of the present application and Comparative Example 1, 2, 3, 4. DETAILED DESCRIPTION

[0051] The present application will be further described by a detailed description of specific embodiments thereof, with reference to the drawings. The drawings are provided to illustrate specific embodiments of the present application and are not intended to limit the scope of the present application. The relative dimensions of the various drawing elements are not necessarily to scale. The relative positions of the various elements in the drawings are intended to represent the relative positions of the elements as described in the specification, and thus can be reversed without departing from the scope of the present disclosure.

[0052] Example 1

[0053] Reference Figure 1 The MicroLED epitaxial structure of the present example includes a 1.8 pm n-type GaN layer 1; a 20 nm n-type Al 0.1 Ga 0.9 N electron injection layer 2; a 75 nm low-doped n-type GaN layer 3; a 199 nm stress release layer 4, wherein the stress release layer 4 includes three periods of n-GaN / u-In 0.05 Ga 0.95 N quantum well with thicknesses of 49 nm and 1 nm, respectively; a 65 nm multi-quantum well layer 5, wherein the multi-quantum well layer 5 includes five periods of n-GaN / u-In 0.15 Ga 0.85N quantum well, thickness is 10 nm and 3 nm respectively; the last quantum well barrier layer 6 with gradual component of 11 nm, wherein the last quantum well barrier layer 6 is composed of x gradually changed n-type In x Ga 1-x N layer 61 and p-type GaN layer 62, thickness is 1 nm and 10 nm respectively; p-type Al 0.15 Ga 0.85 N electron blocking layer 7; high-temperature p-type GaN layer 8 with thickness of 20 nm; p-type GaN electrode contact layer 9 with thickness of 2 nm.

[0054] n-type In x Ga 1-x N layer 61 gradually changes in In component from n end to p end, x gradually changes from 11% to 0%. n-type In x Ga 1-x N layer 61 has n-type doping concentration of 5e17cm 3 .

[0055] P-type GaN layer 62 has p-type doping concentration of 1e18cm 3 ; p-type Al 0.15 Ga 0.85 N electron blocking layer 7 has p-doping concentration of 1e20cm 3 .

[0056] The method for manufacturing the above epitaxial structure is to grow n-type GaN layer, n-type Al 0.1 Ga 0.9 N electron injection layer, low-doped n-type GaN layer, stress release layer 4 and InGaN / GaN multi-quantum well structure on the substrate in sequence by using MOCVD growth process. When growing the last barrier layer, first, n-type In x Ga 1-x N layer with In component x gradually changing from 15% to 0% is grown by adjusting growth temperature, reaction chamber pressure or source flow and other methods, then p-type GaN layer is grown on the n-type In x Ga 1-x N layer; p-type Al 0.15 Ga 0.85 N electron blocking layer, high-temperature p-type GaN layer and p-type GaN electrode contact layer are grown in sequence on the p-type GaN layer.

[0057] Comparative Example 1

[0058] The difference between the MicroLED epitaxial structure of Comparative Example 1 and Example 1 is that the last quantum well barrier layer 6 is composed of n-type GaN with thickness of 10 nm and 10 nm undoped Al 0.1 Ga 0.9 N.

[0059] Except for structure 6, all other parameters of Example 1 and Comparative Example 1 are exactly the same.

[0060] MicroLED devices fabricated based on the epitaxial structures of Example 1 and Comparative Example 1 were tested:

[0061] like Figure 2 As shown, at 1000 A / cm 2 At high current densities, in Comparative Example 1, the strong polarization between the last quantum well barrier layer (LQB) and the electron blocking layer (EBL) results in a relatively low effective conduction band barrier height of only 0.1151 eV for the LQB. This also affects the electron blocking capability of the EBL, ultimately leading to significant electron leakage. In this case, we observe a very high valence band barrier, which blocks hole injection. Such an LQB structure leads to electron leakage and hinders hole injection.

[0062] like Figure 3 As shown, at 1000 A / cm 2 Under high current density, the LQB of Embodiment 1 of the present invention has a higher conduction band barrier height, reaching 0.3534 eV, which is more than three times that of Comparative Example 1. The higher barrier height allows the EBL to function better and effectively suppress electron leakage. In addition, the valence band barrier height is lower than that of Comparative Example 1, only 0.198 eV, which also plays a positive role in hole injection.

[0063] like Figure 4 As shown, at 1000 A / cm 2 At high current densities, comparing the electron-blocking effects of Example 1 and Comparative Example 1, it is evident that the LQB structure of Example 1 is more effective at confining electrons than that of Comparative Example 1. Specifically, the electron concentration in the LQB region of Example 1 is significantly lower than that of Comparative Example 1. Furthermore, due to the unique LQB structure in Example 1, the electron concentration further decreases in the EBL region. This can be interpreted as the designed LQB structure enabling the EBL to more effectively perform its electron-blocking function. After the EBL, the electron concentration in Example 1 is almost four orders of magnitude lower than that in Comparative Example 1, further demonstrating the effectiveness of the designed LQB.

[0064] like Figure 5 As shown, at 1000 A / cm 2 At high current densities, due to the reduction of the LQB valence band barrier in Example 1, hole injection in the quantum well region is significantly improved, and the hole concentration in each quantum well increases, thus proving that the design contributes to hole injection.

[0065] like Figure 6 As shown, at 1000 A / cm 2At high current densities, the radiative recombination rate in Example 1 is significantly higher than that in Comparative Example 1 in each quantum well. This is attributed to better electron blocking and a higher electron concentration in each quantum well. At the same time, the improvement in hole injection also leads to an increase in the hole concentration in the quantum well. The increase in carrier concentration leads to an increase in electron-hole pairs that undergo radiative recombination, and the radiative recombination rate is naturally improved.

[0066] Example 2

[0067] The difference between the MicroLED epitaxial structure in Example 2 and that in Example 1 is that the number of quantum well periods is 1.

[0068] Comparative Example 2

[0069] The difference between the MicroLED epitaxial structure of Comparative Example 2 and Example 2 is that the last quantum well barrier layer 6 consists of 10 nm thick n-type GaN and 10 nm thick undoped Al. 0.1 Ga 0.9 N constitutes the composition.

[0070] like Figure 7 , 8 As shown, at 1000 A / cm 2 Under high current density, the effective conduction band barrier height in Example 2 is higher than that in Comparative Example 2, and the effective valence band barrier is lower than that in Comparative Example 2, which can achieve effective electron blocking and hole injection.

[0071] like Figure 9 As shown, at 1000 A / cm 2 At high current densities, Example 2 exhibits a lower leakage electron level compared to Comparative Example 2, attributed to the higher barrier of LQB and its better ability to block electrons.

[0072] like Figure 10 As shown, at 1000 A / cm 2 At high current densities, the hole concentration in the quantum well in Example 2 is higher, and hole injection is improved.

[0073] like Figure 11 As shown, at 1000 A / cm 2 At high current densities, Example 2 exhibits a higher radiative recombination rate compared to Comparative Example 2, which is attributed to the increased electron and hole concentrations within the quantum well and better carrier matching.

[0074] Example 3

[0075] The difference between the MicroLED epitaxial structure of Example 3 and that of Example 1 is that the number of quantum well periods is 2.

[0076] Comparative Example 3

[0077] The difference between the MicroLED epitaxial structure of Comparative Example 3 and Example 3 is that the last quantum well barrier layer 6 consists of 10 nm thick n-type GaN and 10 nm thick undoped Al. 0.1 Ga 0.9 N constitutes the composition.

[0078] The difference between the MicroLED epitaxial structure of Comparative Example 3 and Example 3 is that the last quantum well barrier layer 6 consists of 10 nm thick n-type GaN and 10 nm thick undoped Al. 0.1 Ga 0.9 N constitutes the composition.

[0079] like Figure 12 , 13 As shown, at 1000 A / cm 2 Under high current density, the effective conduction band barrier height in Example 3 is higher than that in Comparative Example 3, and the effective valence band barrier is lower than that in Comparative Example 2, which can achieve effective electron blocking and hole injection.

[0080] like Figure 14 As shown, at 1000 A / cm 2 At high current densities, Example 3 exhibits a lower leakage electron level compared to Comparative Example 3, attributed to the higher potential barrier of LQB and its better ability to block electrons.

[0081] like Figure 15 As shown, at 1000 A / cm 2 At high current densities, the hole concentration in the quantum well of Example 3 is higher, and hole injection is improved.

[0082] like Figure 16 As shown, at 1000 A / cm 2 At high current densities, Example 3 exhibits a higher radiative recombination rate compared to Comparative Example 3, which is attributed to the increased electron and hole concentrations within the quantum well and better carrier matching.

[0083] Example 4

[0084] The difference between the MicroLED epitaxial structure in Example 4 and that in Example 1 is that the number of quantum well periods is 3.

[0085] Comparative Example 4

[0086] The difference between the MicroLED epitaxial structure of Comparative Example 4 and Example 3 is that the last quantum well barrier layer 6 consists of 10 nm thick n-type GaN and 10 nm thick undoped Al. 0.1 Ga 0.9 N constitutes the composition.

[0087] like Figure 17 , 18 As shown, at 1000 A / cm2 Under high current density, the effective conduction band barrier height in Example 3 is higher than that in Comparative Example 3, and the effective valence band barrier is lower than that in Comparative Example 2, which can achieve effective electron blocking and hole injection.

[0088] like Figure 19 As shown, at 1000 A / cm 2 At high current densities, Example 3 exhibits a lower leakage electron level compared to Comparative Example 3, attributed to the higher potential barrier of LQB and its better ability to block electrons.

[0089] like Figure 20 As shown, at 1000 A / cm 2 At high current densities, the hole concentration in the quantum well of Example 3 is higher, and hole injection is improved.

[0090] like Figure 21 As shown, at 1000 A / cm 2 At high current densities, Example 3 exhibits a higher radiative recombination rate compared to Comparative Example 3, which is attributed to the increased electron and hole concentrations within the quantum well and better carrier matching.

[0091] like Figure 22 As shown, as the injected current density increases from 0 to 1000 A / cm 2 The internal quantum efficiency (IQE) of Comparative Example 1 showed a significant decrease, dropping from a peak of 88.15% to 69.20%, a decrease of 18.95 percentage points. Example 1 exhibited a higher peak IQE of 92.37% with low current injection, and at 1000 A / cm²... 2 At high current densities, the IQE is higher at 82.6%, with an efficiency decrease of only 10.11 percentage points, significantly lower than the 18.95 percentage points in Comparative Example 1. Similarly, similar results can be observed in Examples 2 and 2, 3 and 3, and 4 and 4, all showing a significant improvement in efficiency decrease compared to the corresponding comparative examples. This is clearly attributed to the better electron blocking and hole injection in this design, which improves carrier matching in the quantum well, specifically through an increase in electron-hole pair concentration, and consequently, an increase in radiative recombination rate. All these factors ultimately achieve the desired mitigation of IQE efficiency decrease.

[0092] The results of the above embodiments and comparative examples all demonstrate that using the optimized gradient n-type In x Ga 1-xThe N and P type GaN structure as the LQB layer of the Micro LED can effectively limit the carriers, so that the carriers are more matched and the recombination efficiency in the well is higher. The electroluminescence (EL) intensity, internal quantum efficiency and overall efficiency and light emission level of the Micro LED chip under high current density injection can be improved, thereby providing a solution to the problem of efficiency reduction of the blue Micro LED.

[0093] The above embodiments are only used to further illustrate the Micro LED chip epitaxial structure with a gradual LQB component and the manufacturing method thereof, but the present application is not limited to the embodiments, and any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present application fall within the protection scope of the technical scheme of the present application.

Claims

1. A Micro LED epitaxial structure with gradient LQB composition, characterized in that: This includes InGaN / GaN multiple quantum well structures, which have an n-type side and a p-type side, wherein the last quantum well barrier layer on the p-type side is composed of graded-component n-type In x Ga 1-x It consists of an N-type layer and a p-type GaN layer, with the n-type In layer extending from the n-type side to the p-type side. x Ga 1-x The In composition x of the N layer gradually changes from 15% to 5% to 0%, and an electron blocking layer is provided on the p-type GaN layer.

2. The Micro LED epitaxial structure with gradient LQB composition according to claim 1, characterized in that: The n-type In x Ga 1-x The thickness of the N layer is 1 nm to 5 nm.

3. The Micro LED epitaxial structure with gradient LQB composition according to claim 1, characterized in that: The n-type In x Ga 1-x The n-doping concentration of the N-layer is 1e17cm. 3 ~5e18cm 3 .

4. The Micro LED epitaxial structure with gradient LQB composition according to claim 1, characterized in that: The p-doping concentration of the p-type GaN layer is 1e18cm. 3 ~1e20cm 3 .

5. The Micro LED epitaxial structure with gradient LQB composition according to claim 1, characterized in that: The thickness of the p-type GaN layer is 5 nm to 20 nm.

6. The Micro LED epitaxial structure with gradient LQB composition according to claim 1, characterized in that: The electron blocking layer is a p-type Al. y Ga 1-y N, where y ranges from 0.10 to 0.25, and the p-doping concentration is 1e19cm. 3 ~1e20cm 3 .

7. The Micro LED epitaxial structure with gradient LQB composition according to claim 1, characterized in that: The n-type side is provided with a substrate, an n-type GaN buffer layer, an electron injection layer, a lightly doped n-type GaN layer, and a stress relief layer in sequence, and the multi-quantum well structure is disposed on the stress relief layer.

8. The Micro LED epitaxial structure with gradient LQB composition according to claim 1, characterized in that: It also includes a high-temperature p-type GaN layer and a p-electrode contact layer disposed on the electron blocking layer.

9. The Micro LED epitaxial structure with gradient LQB composition according to claim 1, characterized in that: The InGaN / GaN multiple quantum well structure includes an n-GaN barrier layer and a u-In z Ga 1-z The N-well layer has a z-range of 0.13–0.17; the thickness of each n-GaN barrier layer is 9–12 nm; and the thickness of each u-In layer is... z Ga 1-z The thickness of the N-well layer is 1–5 nm; the n-type doping concentration of GaN is 1e17 cm⁻¹. 3 ~5e18cm 3 .

10. A method for preparing a Micro LED epitaxial structure with a gradient LQB composition as described in any one of claims 1 to 9, characterized in that... include: During the epitaxial growth of InGaN / GaN multiple quantum well structures, when growing the final barrier layer, the In composition x is first gradually increased from 15% to 5% to 0% by adjusting the growth temperature, reaction chamber pressure, or source flow rate to form n-type In. x Ga 1-x N layers, then in n-type In x Ga 1-x A p-type GaN layer is grown on the N-layer; an electron blocking layer is grown on the p-type GaN layer.

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