Green light Micro-LED epitaxial structure and preparation method thereof, and green light Micro-LED

Abstract

The invention discloses a green light Micro-LED epitaxial structure, a preparation method of the green light Micro-LED epitaxial structure and a green light Micro-LED, and relates to the field of semiconductor photoelectric devices. The epitaxial structure sequentially comprises a substrate, a buffer layer, a non-doped GaN layer, an N-type GaN layer, an electron transport layer, a multi-quantum well layer and a P-type GaN layer; the electron transport layer sequentially comprises a first sub-layer, a second sub-layer, a third sub-layer, a fourth sub-layer, a fifth sub-layer and a sixth sub-layer; the first sub-layer comprises a non-doped Al-containing nitride layer and a Si-doped Al-containing nitride layer which are alternately stacked; the second sub-layer, the third sub-layer and the fourth sub-layer are all C and Si co-doped Ga-containing nitride layers, the fifth sub-layer is a Si-doped AlGaN layer, and the sixth sub-layer comprises Si-doped GaN layers and InGaN layers which are alternately stacked; the Si doping concentration of the second sub-layer, the third sub-layer and the fourth sub-layer is greater than the Si doping concentration of the Si-doped Al nitride layer; and the Si doping concentrations of the second sub-layer, the third sub-layer and the fourth sub-layer are respectively greater than the C doping concentrations thereof. By implementing the invention, the lighting effect and the wavelength uniformity can be improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor optoelectronic devices, and particularly to a green Micro-LED epitaxial structure, a preparation method thereof, and a green Micro-LED. Background Art

[0002] Micro-LED generally refers to a chip with a size less than 100 μm. It has excellent performance and low power consumption, and is the latest and best application technology in the foreseeable multi-display scenarios at the current stage. However, the working current density of Micro-LED is generally between 0.1 and 2 A / cm 2 . Under such a small current density, how to achieve uniform current distribution and how to improve the light-emitting efficiency become extremely important issues. On the one hand, since the electron mobility in the GaN material system is much greater than the hole mobility, this leads to a low matching degree of electron carriers and hole carriers in the multi-quantum well layer, resulting in low light-emitting efficiency; especially in the green Micro-LED chip with a high In-component quantum well, due to a higher lattice mismatch degree and greater compressive stress between the quantum well layer and the quantum barrier layer, the recombination efficiency is worse and the light-emitting efficiency is low. On the other hand, since the resistivity of N-type GaN is higher than that of the transparent conductive layer (ITO layer) in the LED structure, it is also not conducive to current spreading. Currently, one of the main methods to solve the electron-hole mismatch is to introduce a high-barrier structure after the N-type GaN layer to reduce the electron migration rate, but this structure often means a further deterioration of the current distribution effect and a reduction in light-emitting uniformity. When used as a display screen, it will cause large display differences between pixels and poor color consistency. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a green Micro-LED epitaxial structure with high light-emitting efficiency and good light-emitting uniformity.

[0004] Another technical problem to be solved by the present invention is to provide a green Micro-LED.

[0005] To solve the above problems, the present invention discloses a green Micro-LED epitaxial structure, which includes a substrate, a buffer layer, an undoped GaN layer, an N-type GaN layer, an electron transport layer, a multi-quantum well layer, and a P-type GaN layer that are sequentially stacked on the substrate; Among them, the electron transport layer includes a first sub-layer, a second sub-layer, a third sub-layer, a fourth sub-layer, a fifth sub-layer, and a sixth sub-layer that are sequentially stacked on the N-type GaN layer. The first sub-layer includes an undoped Al-containing nitride layer and a Si-doped Al-containing nitride layer that are alternately stacked; the second sub-layer, the third sub-layer, and the fourth sub-layer are all C and Si co-doped Ga-containing nitride layers; the fifth sub-layer is a Si-doped AlGaN layer, and the sixth sub-layer includes a Si-doped GaN layer and an InGaN layer that are alternately stacked; The Si doping concentrations of the second sub-layer, the third sub-layer, and the fourth sub-layer are all greater than the Si doping concentration of the Si-doped Al-containing nitride layer; the Si doping concentrations in the second sub-layer, the third sub-layer, and the fourth sub-layer are respectively greater than their C doping concentrations.

[0006] As an improvement of the above technical solution, the undoped Al-containing nitride layer is an undoped AlN layer, an undoped AlGaN layer, or an undoped AlInGaN layer; and / or The Si-doped Al-containing nitride layer is a Si-doped AlN layer, a Si-doped AlGaN layer, or a Si-doped AlInGaN layer; and / or The Ga-containing nitride layer is a GaN layer, an AlGaN layer, an AlInGaN layer, an InGaN layer, a BGaN layer, or a BInGaN layer.

[0007] As an improvement of the above technical solution, the undoped Al-containing nitride layer is an undoped AlN layer, the Si-doped Al-containing nitride layer is a Si-doped AlGaN layer, and the Ga-containing nitride layer is a GaN layer; or The undoped Al-containing nitride layer is an undoped AlN layer, the Si-doped Al-containing nitride layer is a Si-doped AlInGaN layer, and the Ga-containing nitride layer is a BGaN layer.

[0008] As an improvement of the above technical solution, the undoped Al-containing nitride layer is an undoped AlGaN layer, the Si-doped Al-containing nitride layer is a Si-doped AlInGaN layer, and the Ga-containing nitride layer is an InGaN layer; or The undoped Al-containing nitride layer is an undoped AlGaN layer, the Si-doped Al-containing nitride layer is a Si-doped AlGaN layer, and the Ga-containing nitride layer is an AlGaN layer.

[0009] As an improvement of the above technical solution, the thickness of the first sub-layer is 50 nm to 500 nm, and the thickness ratio of the undoped Al-containing nitride layer to the Si-doped Al-containing nitride layer is 1:2 to 1:5; the Si doping concentration of the Si-doped Al-containing nitride layer is 1×10 17 cm -3 ~1×1018 cm -3 ; The number of periods of the first sub-layer is 1 to 10; and / or The total thickness of the second sub-layer, the third sub-layer, and the fourth sub-layer is 50 nm to 500 nm, and the thickness ratio of the second sub-layer, the third sub-layer, and the fourth sub-layer is 1:1:1 to 10:1:10; and / or The C doping concentration of the second sub-layer, the third sub-layer, and the fourth sub-layer is 1×10 17 cm -3 ~1×10 18 cm -3 , and the Si doping concentration is 3×10 18 cm -3 ~1×10 19 cm -3 ; and / or The thickness of the fifth sub-layer is 10 nm to 100 nm, and its Si doping concentration is 3×10 18 cm -3 ~8×10 18 cm -3 , and the proportion of its Al component is 0.01 to 0.3; and / or The thickness of the Si-doped GaN layer is 5 nm to 20 nm, and its Si doping concentration is 1×10 17 cm -3 ~1×10 18 cm -3 ; and / or The thickness of the InGaN layer is 1 nm to 5 nm, and the proportion of its In component is 0.01 to 0.2; and / or The number of periods of the sixth sub-layer is 3 to 20.

[0010] As an improvement to the above technical solution, the Si doping concentration of the third sub-layer > the Si doping concentration of the second sub-layer, and the Si doping concentration of the second sub-layer is the same as the Si doping concentration of the fourth sub-layer; and / or The C doping concentrations of the second sub-layer, the third sub-layer, and the fourth sub-layer are the same.

[0011] As an improvement to the above technical solution, the Si doping concentration of the third sub-layer > the Si doping concentration of the fifth sub-layer > the Si doping concentration of the second sub-layer > the Si doping concentration of the first sub-layer, and the Si doping concentration of the second sub-layer is the same as the Si doping concentration of the fourth sub-layer.

[0012] As an improvement to the above technical solution, in the fifth sub-layer, the proportion of the Al component increases along the growth direction of the epitaxial structure.

[0013] Correspondingly, the present invention also discloses a method for preparing a green Micro-LED epitaxial structure for preparing the above-mentioned green Micro-LED epitaxial structure, which includes: Providing a substrate, and sequentially growing a buffer layer, an undoped GaN layer, an N-type GaN layer, an electron transport layer, a multi-quantum well layer, and a P-type GaN layer on the substrate; Wherein, the electron transport layer includes a first sub-layer, a second sub-layer, a third sub-layer, a fourth sub-layer, a fifth sub-layer, and a sixth sub-layer sequentially stacked on the N-type GaN layer. The first sub-layer includes an alternately stacked undoped Al-containing nitride layer and a Si-doped Al-containing nitride layer; the second sub-layer, the third sub-layer, and the fourth sub-layer are all C, Si co-doped Ga-containing nitride layers; the fifth sub-layer is a Si-doped AlGaN layer, and the sixth sub-layer includes an alternately stacked Si-doped GaN layer and an InGaN layer; The Si doping concentrations of the second sub-layer, the third sub-layer, and the fourth sub-layer are all greater than the Si doping concentration of the Si-doped Al-containing nitride layer; the Si doping concentrations of the second sub-layer, the third sub-layer, and the fourth sub-layer are respectively greater than their C doping concentrations.

[0014] Correspondingly, the present invention also discloses a green Micro-LED, which includes the above-mentioned green Micro-LED epitaxial structure.

[0015] Implementing the present invention has the following beneficial effects: In a green Micro-LED epitaxial structure according to an embodiment of the present invention, an electron transport layer is introduced between the N-type GaN layer and the multi-quantum well layer. The electron transport layer includes a first sub-layer, a second sub-layer, a third sub-layer, a fourth sub-layer, a fifth sub-layer, and a sixth sub-layer that are sequentially stacked on the N-type GaN layer. The first sub-layer includes an undoped Al-containing nitride layer and a Si-doped Al-containing nitride layer that are alternately stacked; the second sub-layer, the third sub-layer, and the fourth sub-layer are all C and Si co-doped Ga-containing nitride layers; the fifth sub-layer is a Si-doped AlGaN layer, and the sixth sub-layer includes a Si-doped GaN layer and an InGaN layer that are alternately stacked; the Si doping concentration of the second sub-layer, the third sub-layer, and the fourth sub-layer is greater than the Si doping concentration of the Si-doped Al-containing nitride layer. Al is introduced into both the first sub-layer and the fifth sub-layer, and its potential barrier is relatively high, which can slow down the movement speed of electron carriers, improve the radiative recombination efficiency of electron carriers and hole carriers in the multi-quantum well layer, and improve the light-emitting efficiency. However, the introduction of Al will also weaken the current distribution uniformity. Therefore, in this embodiment, a C and Si co-doped Ga-containing nitride layer is also introduced as the second sub-layer, the third sub-layer, and the fourth sub-layer, and the C doping concentration is controlled to be less than the Si doping concentration. Through low-concentration C doping, the Fermi level can be reduced, the Si incorporation efficiency can be promoted, and thus the overall resistivity can be reduced and the current distribution can be optimized; C doping can also promote the climb of edge dislocations, and C and Si co-doping can promote the formation of V-shaped pits, enabling hole carriers to enter deeper quantum well layers through the side walls of the V-shaped pits, not only improving the radiative recombination efficiency, but also optimizing the current distribution, so that better current spreading performance is still achieved in the case of introducing the first sub-layer and the fourth sub-layer, and the light-emitting uniformity is improved. In the sixth sub-layer, a structure in which a Si-doped GaN layer and an InGaN layer are alternately formed with an alternating potential barrier / quantum well is adopted to further optimize the electron distribution, and it is also beneficial to release stress, reduce the polarization effect of the subsequent grown multi-quantum well layer, and improve the light-emitting efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic structural diagram of a green Micro-LED epitaxial structure according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below.

[0018] See Figure 1 , an embodiment of the present invention discloses a green Micro-LED epitaxial structure, which includes a substrate 100, a buffer layer 200, an undoped GaN layer 300, an N-type GaN layer 400, an electron transport layer 500, a multi-quantum well layer 600, and a P-type GaN layer 700 that are sequentially stacked on the substrate 100.

[0019] Among them, the electron transport layer 500 includes a first sub-layer 510, a second sub-layer 520, a third sub-layer 530, a fourth sub-layer 540, a fifth sub-layer 550, and a sixth sub-layer 560 that are sequentially stacked on the N-type GaN layer 400. The first sub-layer 510 includes an undoped Al-containing nitride layer 511 and a Si-doped Al-containing nitride layer 512 that are alternately stacked; the second sub-layer 520, the third sub-layer 530, and the fourth sub-layer 540 are all Ga-containing nitride layers co-doped with C and Si; the fifth sub-layer 550 is a Si-doped AlGaN layer, and the sixth sub-layer 560 includes a Si-doped GaN layer 561 and an InGaN layer 562 that are alternately stacked; the Si doping concentrations of the second sub-layer 520, the third sub-layer 530, and the fourth sub-layer 540 are all greater than the Si doping concentration of the Si-doped Al-containing nitride layer 512; the Si doping concentrations of the second sub-layer 520, the third sub-layer 530, and the fourth sub-layer 540 are respectively greater than their C doping concentrations. Specifically, Al is introduced into both the first sub-layer 510 and the fifth sub-layer 550, and its potential barrier is relatively high, which can slow down the movement speed of electron carriers, improve the radiative recombination efficiency of electron carriers and hole carriers in the multi-quantum well layer 600, and improve the luminous efficiency. However, the introduction of Al will also weaken the current distribution uniformity. Therefore, in this embodiment, a Ga-containing nitride layer co-doped with C and Si is also introduced as the second sub-layer 520, the third sub-layer 530, and the fourth sub-layer 540, and the C doping concentration is controlled to be less than the Si doping concentration. Through low-concentration C doping, the Fermi level can be lowered, the Si incorporation efficiency can be promoted, and thus the overall resistivity can be reduced and the current distribution can be optimized; C doping can also promote the climb of edge dislocations, and the co-doping of C and Si can promote the formation of V-shaped pits, so that hole carriers enter deeper quantum well layers through the side walls of the V-shaped pits, which not only improves the radiative recombination efficiency, but also optimizes the current distribution, so that better current spreading performance is still achieved in the case of introducing the first sub-layer 510 and the fourth sub-layer 540. The Si-doped GaN layer 561 and the InGaN layer 562 in the sixth sub-layer 560 are alternately formed into a structure with alternating potential barriers / wells, which further optimizes the electron distribution, and is also beneficial to releasing stress, reducing the polarization effect of the subsequently grown multi-quantum well layer 600, and improving the luminous efficiency.

[0020] Specifically, in some embodiments, the undoped Al-containing nitride layer 511 is an undoped AlN layer, an undoped AlGaN layer, or an undoped AlInGaN layer, but is not limited thereto. Preferably, the undoped Al-containing nitride layer 511 is an undoped AlN layer or an undoped AlGaN layer, and the potential barrier of such an undoped Al-containing nitride layer 511 is higher, which is beneficial to further reducing the migration rate of electron carriers.

[0021] Specifically, in some embodiments, the Si-containing Al nitride layer 512 is an Si-doped AlN layer, an Si-doped AlGaN layer, or an Si-doped AlInGaN layer, but is not limited thereto. Preferably, the Si-containing Al nitride layer 512 is an undoped AlN layer or an undoped AlGaN layer, and such an Si-containing Al nitride layer 512 has a higher barrier, which is beneficial to further reducing the migration rate of electron carriers.

[0022] Specifically, in some embodiments, the Ga-containing nitride layer is a GaN layer, an AlGaN layer, an AlInGaN layer, an InGaN layer, a BGaN layer, or a BInGaN layer, but is not limited thereto. Preferably, the Ga-containing nitride layer is a GaN layer, an AlGaN layer, an InGaN layer, or a BGaN layer, and based on these Ga-containing nitride layers, the current distribution can be optimized.

[0023] Preferably, through a large number of studies, it is found that the following four combinations have better luminous efficiency and better current spreading performance: (1) The undoped Al-containing nitride layer 511 is an undoped AlN layer, the Si-containing Al nitride layer 512 is an Si-doped AlGaN layer, and the Ga-containing nitride layer is a GaN layer. Based on this embodiment, the proportion of the Al component in the Si-doped AlGaN layer ≤ 0.2. Preferably, the proportion of the Al component in the Si-doped AlGaN layer is 0.05 - 0.15.

[0024] (2) The undoped Al-containing nitride layer 511 is an undoped AlN layer, the Si-containing Al nitride layer 512 is an Si-doped AlInGaN layer, and the Ga-containing nitride layer is a BGaN layer. Based on this embodiment, the proportion of the Al component in the Si-doped AlInGaN layer ≥ 0.2, and the proportion of the In component ≤ 0.1; and the proportion of the B component in the Ga-containing nitride layer (BGaN layer) ≤ 0.1. More preferably, the proportion of the Al component in the Si-doped AlInGaN layer is 0.3 - 0.5, the proportion of the In component is 0.05 - 0.1; and the proportion of the B component in the BGaN layer is 0.02 - 0.06.

[0025] (3) The undoped Al-containing nitride layer 511 is an undoped AlGaN layer, the Si-doped Al-containing nitride layer 512 is a Si-doped AlInGaN layer, and the Ga-containing nitride layer is an InGaN layer. Based on this embodiment, the proportion of the Al component in the undoped AlGaN layer ≥ 0.1, the proportion of the Al component in the Si-doped AlInGaN ≥ 0.1, and the proportion of the In component ≤ 0.15; and the proportion of the In component in the Ga-containing nitride layer (InGaN layer) ≤ 0.15. More preferably, the proportion of the Al component in the undoped AlGaN layer is 0.1 - 0.15, the proportion of the Al component in the Si-doped AlInGaN layer is 0.1 - 0.2, and the proportion of the In component is 0.08 - 0.12; and the proportion of the In component in the InGaN layer is 0.1 - 0.15.

[0026] (4) The undoped Al-containing nitride layer 511 is an undoped AlGaN layer, the Si-doped Al-containing nitride layer 512 is a Si-doped AlGaN layer, and the Ga-containing nitride layer is an AlGaN layer. Based on this embodiment, the proportion of the Al component in the undoped AlGaN layer ≥ 0.1, the proportion of the Al component in the Si-doped AlGaN ≥ 0.1; and the proportion of the Al component in the Ga-containing nitride layer (AlGaN layer) ≤ 0.08. More preferably, the proportion of the Al component in the undoped AlGaN layer is 0.1 - 0.15, the proportion of the Al component in the Si-doped AlGaN layer is 0.1 - 0.15, and the proportion of the Al component in the Ga-containing nitride layer (AlGaN layer) is 0.02 - 0.08.

[0027] Specifically, in some embodiments, the thickness of the first sub-layer 510 is 50 nm - 500 nm, and its number of periods is 1 - 10. Preferably, the thickness of the first sub-layer 510 is 100 nm - 500 nm, and its number of periods is 3 - 8.

[0028] Specifically, in some embodiments, the thickness ratio of the undoped Al-containing nitride layer 511 to the Si-doped Al-containing nitride layer 512 is 1:2 - 1:5; the Si doping concentration of the Si-doped Al-containing nitride layer 512 is 1×10 17 cm -3 ~ 1×10 18 cm -3 . Preferably, the thickness ratio of the undoped Al-containing nitride layer 511 to the Si-doped Al-containing nitride layer 512 is 1:3 - 1:5; the Si doping concentration of the Si-doped Al-containing nitride layer 512 is 1×10 17 cm -3 ~ 7×10 17 cm -3 .

[0029] Specifically, in some embodiments, the total thickness of the second sub-layer 520, the third sub-layer 530, and the fourth sub-layer 540 is 50 nm to 500 nm, wherein the thickness ratio of the second sub-layer 520, the third sub-layer 530, and the fourth sub-layer 540 is (1 to 10):1:(1 to 10). Preferably, the total thickness of the second sub-layer 520, the third sub-layer 530, and the fourth sub-layer 540 is 80 nm to 200 nm, wherein the thickness ratio of the second sub-layer 520, the third sub-layer 530, and the fourth sub-layer 540 is (1 to 5):1:(5 to 8).

[0030] Specifically, in some embodiments, the C doping concentrations of the second sub-layer 520, the third sub-layer 530, and the fourth sub-layer 540 are the same or different, and the Si doping concentrations are the same or different, but it is necessary to control the C doping concentration to be lower than the Si doping concentration. If the C doping concentration is higher than the Si doping concentration, C may form donor doping, which instead increases the resistivity and makes the current distribution more concentrated. Specifically, the Si doping concentration of the second sub-layer 520 is greater than its C doping concentration, the Si doping concentration of the third sub-layer 530 is greater than its C doping concentration, and the Si doping concentration of the fourth sub-layer 540 is greater than its C doping concentration.

[0031] More specifically, in some embodiments, the C doping concentrations of the second sub-layer 520, the third sub-layer 530, and the fourth sub-layer 540 are all 1×10 17 cm -3 ~1×10 18 cm -3 , and the Si doping concentrations are all 3×10 18 cm -3 ~1×10 19 cm -3 . Preferably, the C doping concentrations of the second sub-layer 520, the third sub-layer 530, and the fourth sub-layer 540 are 1.5×10 17 cm -3 ~5×10 17 cm -3 , and the Si doping concentrations are all 3×10 18 cm -3 ~9×10 18 cm -3 . It should be noted that the C doping concentrations of the second sub-layer 520, the third sub-layer 530, and the fourth sub-layer 540 are the same or different, and the Si doping concentrations of the second sub-layer 520, the third sub-layer 530, and the fourth sub-layer 540 are the same or different.

[0032] Specifically, in some embodiments, the thickness of the fifth sub-layer 550 is 10 nm to 100 nm, and its Si doping concentration is 3×10 18 cm -3 ~8×10 18 cm-3 ; The proportion of the Al component is 0.01 to 0.3. Preferably, the thickness of the fifth sub-layer 550 is 20 nm to 50 nm, and its Si doping concentration is 5×10 18 cm -3 ~8×10 18 cm -3 ; The proportion of the Al component is 0.05 to 0.2.

[0033] Specifically, in some embodiments, the number of periods of the sixth sub-layer 560 is 3 to 20. The thickness of the Si-doped GaN layer 561 is 5 nm to 20 nm, and its Si doping concentration is 1×10 17 cm -3 ~1×10 18 cm -3 ; The thickness of the InGaN layer 562 is 1 nm to 5 nm, and the proportion of its In component is 0.01 to 0.2. Preferably, the number of periods of the sixth sub-layer 560 is 5 to 15. The thickness of the Si-doped GaN layer 561 is 5 nm to 15 nm, and its Si doping concentration is 1×10 17 cm -3 ~5×10 17 cm -3 ; The thickness of the InGaN layer 562 is 2 nm to 5 nm, and the proportion of its In component is 0.05 to 0.12.

[0034] Specifically, the substrate 100 is a sapphire substrate or a silicon substrate, but is not limited thereto.

[0035] Specifically, the buffer layer 200 is an AlN layer or an AlGaN layer, but is not limited thereto. The thickness of the buffer layer 200 is 30 nm to 80 nm.

[0036] Specifically, the thickness of the undoped GaN layer 300 is 1 μm to 3 μm.

[0037] Specifically, the doping element of the N-type GaN layer 400 is Si, but is not limited thereto. The Si doping concentration in the N-type GaN layer 400 is 1×10 18 cm -3 ~5×10 19 cm -3 , and its thickness is 1 μm to 3 μm.

[0038] Specifically, the multi-quantum well layer 600 includes alternately stacked InGaN quantum well layers and GaN quantum barrier layers, and its number of periods is 3 to 15. The thickness of a single InGaN quantum well layer is 3 nm to 5 nm, and the thickness of a single GaN quantum barrier layer is 5 nm to 15 nm.

[0039] Specifically, the doping element of the P-type GaN layer 700 is Mg, but it is not limited thereto. The doping concentration of Mg in the P-type GaN layer 700 is 1×10 19 cm -3 ~5×10 20 cm -3 , and its thickness is 20 nm to 200 nm.

[0040] Preferably, in some embodiments of the present invention, the Si doping concentration of the third sub-layer 530 > the Si doping concentration of the second sub-layer 520, and the Si doping concentration of the second sub-layer 520 is the same as the Si doping concentration of the fourth sub-layer 540; and the C doping concentrations of the second sub-layer 520, the third sub-layer 530, and the fourth sub-layer 540 are the same. By controlling the relationship of the Si doping concentrations of the second sub-layer 520, the third sub-layer 530, and the fourth sub-layer 540, the distribution of electrons can be effectively adjusted, current congestion can be avoided, and the light emission uniformity and light emission efficiency can be improved. By controlling the C doping concentration, the distribution of V-shaped pits is optimized, further promoting the uniformity of current distribution.

[0041] More preferably, the Si doping concentration of the third sub-layer 530 > the Si doping concentration of the fifth sub-layer 550 > the Si doping concentration of the second sub-layer 520 > the Si doping concentration of the first sub-layer 510, and the Si doping concentration of the second sub-layer 520 is the same as the Si doping concentration of the fourth sub-layer 540.

[0042] Preferably, in some embodiments of the present invention, in the fifth sub-layer 550, the proportion of the Al component increases along the growth direction of the epitaxial structure, and more preferably, it increases linearly. By adopting this method, on the one hand, the crystal quality of the fifth sub-layer 550 can be improved, and the flow rate of electron carriers can be further delayed; on the other hand, the uniform distribution of electron carriers can also be effectively optimized.

[0043] Correspondingly, the present invention also provides a method for preparing a green Micro-LED epitaxial structure for preparing the above-mentioned green Micro-LED epitaxial structure, which specifically includes the following steps: S1: Provide a substrate; S2: Sequentially grow a buffer layer, an undoped GaN layer, an N-type GaN layer, an electron transport layer, a multi-quantum well layer, and a P-type GaN layer on the substrate; Specifically, the electron transport layer includes a first sub-layer, a second sub-layer, a third sub-layer, a fourth sub-layer, a fifth sub-layer, and a sixth sub-layer that are sequentially stacked on the N-type GaN layer. The first sub-layer includes an undoped aluminum-containing nitride layer and a Si-doped aluminum-containing nitride layer that are alternately stacked; the second sub-layer, the third sub-layer, and the fourth sub-layer are all C- and Si-codoped gallium-containing nitride layers; the fifth sub-layer is a Si-doped AlGaN layer, and the sixth sub-layer includes an alternately stacked Si-doped GaN layer and an InGaN layer. The electron transport layer in the present invention can reduce the transport speed of electron carriers, optimize their distribution, and also promote hole injection into a deeper multi-quantum well layer. It not only effectively improves the light-emitting efficiency but also ensures the uniformity of current spreading and improves the light-emitting uniformity.

[0044] Specifically, in some embodiments of the present invention, step S2 includes: S21: Growing a buffer layer on the substrate; Specifically, in some embodiments, an AlN layer is grown by PVD as the buffer layer.

[0045] S22: Growing an undoped GaN layer on the buffer layer; Specifically, in some embodiments, an undoped GaN layer is grown by MOCVD, and its growth temperature is 1000°C to 1200°C, and the growth pressure is 100 torr to 500 torr.

[0046] S23: Growing an N-type GaN layer on the undoped GaN layer; Specifically, in some embodiments, an N-type GaN layer is grown by MOCVD, and its growth temperature is 1100°C to 1200°C, and the growth pressure is 100 torr to 500 torr.

[0047] S24: Growing an electron transport layer on the N-type GaN layer; Specifically, in some embodiments, the first sub-layer, the second sub-layer, the third sub-layer, the fourth sub-layer, the fifth sub-layer, and the sixth sub-layer are sequentially grown by MOCVD to obtain the electron transport layer.

[0048] Among them, the growth temperature of the first sub-layer is 1000°C to 1200°C, and the growth pressure is 50 torr to 300 torr. The growth temperature of the second sub-layer, the third sub-layer, and the fourth sub-layer is 800°C to 1200°C, and the growth pressure is 50 torr to 500 torr. The growth temperature of the fifth sub-layer is 800°C to 1000°C, and the growth pressure is 50 torr to 300 torr. The growth pressure of the sixth sub-layer is 800°C to 900°C, and the growth pressure is 50 torr to 500 torr.

[0049] S25: Growing a multi-quantum well layer on the electron transport layer; Specifically, in some embodiments, an InGaN quantum well layer and a GaN quantum barrier layer are periodically grown on the electron transport layer by MOCVD until a multi-quantum well layer is obtained.

[0050] Among them, the growth temperature of the InGaN quantum well layer is 730 °C to 800 °C, and the growth pressure is 100 torr to 300 torr. The growth temperature of the GaN quantum barrier layer is 850 °C to 1000 °C, and the growth pressure is 100 torr to 300 torr.

[0051] S25: Grow a P-type GaN layer on the multi-quantum well layer; Specifically, in an embodiment of the present invention, a P-type GaN layer is grown by MOCVD, the growth temperature is 950 °C to 1000 °C, and the growth pressure is 100 torr to 300 torr.

[0052] The present invention will be further described below with specific examples: Example 1 This embodiment provides a green Micro-LED epitaxial structure, which includes a substrate, a buffer layer, an undoped GaN layer, an N-type GaN layer, an electron transport layer, a multi-quantum well layer, and a P-type GaN layer that are sequentially stacked on the substrate.

[0053] Among them, the substrate is a sapphire substrate, the buffer layer is an AlN layer with a thickness of 50 nm, and the thickness of the undoped GaN layer is 2 μm. The Si doping concentration of the N-type GaN layer is 6.8×10 18 cm -3 , and its thickness is 3 μm.

[0054] Among them, the electron transport layer includes a first sub-layer, a second sub-layer, a third sub-layer, a fourth sub-layer, a fifth sub-layer, and a sixth sub-layer that are sequentially stacked on the N-type GaN layer.

[0055] The first sub-layer includes an alternately stacked undoped Al 0.3 Ga 0.7 N layer and a Si-doped Al 0.5 In 0.05 Ga 0.45 N layer, and its number of periods is 5. The thickness of the first sub-layer is 100 nm, and the thickness ratio of the undoped Al 0.3 Ga 0.7 N layer to the Si-doped Al 0.5 In 0.05 Ga 0.45 N layer is 1:4. The doping concentration of the Si-doped Al 0.5 In 0.05 Ga 0.45 N layer is 5×10 17 cm-3 .

[0056] The second sub-layer is a C, Si co-doped GaN layer, with a C doping concentration of 2.5×10 17 cm -3 , and an Si doping concentration of 5.5×10 18 cm -3 . The third sub-layer is a C, Si co-doped GaN layer, with a C doping concentration of 2.5×10 17 cm -3 , and an Si doping concentration of 5.5×10 18 cm -3 . The fourth sub-layer is a C, Si co-doped Al 0.05 Ga 0.95 N layer, with a C doping concentration of 3×10 17 cm -3 , and an Si doping concentration of 5.5×10 18 cm -3 . The total thickness of the second sub-layer, the third sub-layer, and the fourth sub-layer is 200 nm, and the thickness ratio of the three is 2:1:2.

[0057] The fifth sub-layer is an Si-doped AlGaN layer, with a thickness of 35 nm and an Si doping concentration of 3×10 18 cm -3 ; the proportion of its Al component is 0.1.

[0058] The sixth sub-layer includes an alternately stacked Si-doped GaN layer and InGaN layer, with 12 periods. The thickness of the Si-doped GaN layer is 10 nm, and the Si doping concentration is 6.5×10 17 cm -3 ; the thickness of the InGaN layer is 4 nm, and the proportion of its In component is 0.1.

[0059] Among them, the multi-quantum well layer includes an alternately stacked InGaN quantum well layer and GaN quantum barrier layer, with 10 periods. Among them, the proportion of the In component in the InGaN quantum well layer is 0.3, and its thickness is 3 nm. The thickness of the GaN quantum barrier layer is 10 nm.

[0060] Among them, the Mg doping concentration in the P-type GaN layer is 8×10 19 cm -3 , and its thickness is 100 nm.

[0061] Example 2 This example provides a green Micro-LED epitaxial structure, which is different from that of Example 1 in that: the electron transport layer is different. Specifically as follows: The first sub-layer includes an alternately stacked undoped AlN layer and Si-doped Al 0.12 Ga0.88 N layers, with a period number of 4. The thickness of the first sub-layer is 80 nm, and the thickness ratio of the undoped AlN layer to the Si-doped Al 0.12 Ga 0.88 N layer is 1:3. The doping concentration of the Si-doped Al 0.12 Ga 0.88 N layer is 8.5×10 17 cm -3 .

[0062] The second sub-layer, the third sub-layer, and the fourth sub-layer are all C and Si co-doped GaN layers, with a C doping concentration of 2.5×10 17 cm -3 , and a Si doping concentration of 5.5×10 18 cm -3 . The total thickness of the second sub-layer, the third sub-layer, and the fourth sub-layer is 200 nm, and the thickness ratio of the three is 2:1:2.

[0063] The fifth sub-layer is a Si-doped AlGaN layer, with a thickness of 35 nm and a Si doping concentration of 3×10 18 cm -3 ; the proportion of its Al component is 0.1.

[0064] The sixth sub-layer includes alternately stacked Si-doped GaN layers and InGaN layers, with a period number of 12. The thickness of the Si-doped GaN layer is 10 nm, and the Si doping concentration is 6.5×10 17 cm -3 ; the thickness of the InGaN layer is 4 nm, and the proportion of its In component is 0.1.

[0065] The rest are the same as in Example 1.

[0066] Example 3 This example provides a green Micro-LED epitaxial structure, which is different from that in Example 1 in that: the electron transport layer is different. Specifically as follows: The first sub-layer includes alternately stacked undoped AlN layers and Si-doped Al 0.35 In 0.08 Ga 0.57 N layers, with a period number of 4. The thickness of the first sub-layer is 80 nm, and the thickness ratio of the undoped AlN layer to the Si-doped Al 0.35 In 0.08 Ga 0.57 N layer is 1:3. The doping concentration of the Si-doped Al 0.35 In 0.08 Ga 0.57 N layer is 8×10 17 cm -3 .

[0067] The second sub-layer, the third sub-layer, and the fourth sub-layer are all C and Si co-doped BGaN layers, with a C doping concentration of 3×10 17 cm -3 , and an Si doping concentration of 8.5×10 18 cm -3 . The total thickness of the second sub-layer, the third sub-layer, and the fourth sub-layer is 200 nm, and the thickness ratio of the three is 2:1:2.

[0068] The fifth sub-layer is an Si-doped AlGaN layer with a thickness of 35 nm and an Si doping concentration of 3×10 18 cm -3 ; the proportion of its Al component is 0.1.

[0069] The sixth sub-layer includes alternately stacked Si-doped GaN layers and InGaN layers, with 12 periods. The thickness of the Si-doped GaN layer is 10 nm, and the Si doping concentration is 6.5×10 17 cm -3 ; the thickness of the InGaN layer is 4 nm, and the proportion of its In component is 0.1.

[0070] The rest are the same as in Example 1.

[0071] Example 4 This example provides a green Micro-LED epitaxial structure, which is different from that in Example 1 in that: the electron transport layer is different. The details are as follows: The first sub-layer includes alternately stacked undoped Al 0.12 Ga 0.88 N layers and Si-doped Al 0.15 In 0.1 Ga 0.75 N layers, with 4 periods. The thickness of the first sub-layer is 80 nm, and the thickness ratio of the undoped Al 0.12 Ga 0.88 N layer to the Si-doped Al 0.15 In 0.1 Ga 0.75 N layer is 1:3. The doping concentration of the Si-doped Al 0.15 In 0.1 Ga 0.75 N layer is 7×10 17 cm -3 .

[0072] The second sub-layer, the third sub-layer, and the fourth sub-layer are all C and Si co-doped In 0.11 Ga 0.89 N layers, with a C doping concentration of 2×10 17 cm -3 , and an Si doping concentration of 7×10 18 cm -3The total thickness of the second sub-layer, the third sub-layer, and the fourth sub-layer is 200 nm, and the thickness ratio of the three is 2:1:2.

[0073] The fifth sub-layer is an Si-doped AlGaN layer with a thickness of 35 nm and an Si doping concentration of 3×10 18 cm -3 ; the proportion of its Al component is 0.1.

[0074] The sixth sub-layer includes alternating layers of Si-doped GaN and InGaN, and the number of periods is 12. The thickness of the Si-doped GaN layer is 10 nm, and the Si doping concentration is 6.5×10 17 cm -3 ; the thickness of the InGaN layer is 4 nm, and the proportion of its In component is 0.1.

[0075] The rest are the same as in Example 1.

[0076] Example 5 This example provides a green Micro-LED epitaxial structure, which is different from that in Example 1 in that: the electron transport layer is different. The details are as follows: The first sub-layer includes alternating layers of undoped Al 0.12 Ga 0.88 N layer and Si-doped Al 0.15 Ga 0.85 N layer, and the number of periods is 4. The thickness of the first sub-layer is 80 nm, and the thickness ratio of the undoped Al 0.12 Ga 0.88 N layer to the Si-doped Al 0.15 Ga 0.85 N layer is 1:3. The doping concentration of the Si-doped Al 0.15 Ga 0.85 N layer is 5×10 17 cm -3 .

[0077] The second sub-layer, the third sub-layer, and the fourth sub-layer are all C and Si co-doped Al 0.06 Ga 0.94 N layers, with a C doping concentration of 2×10 17 cm -3 , and an Si doping concentration of 8×10 18 cm -3 The total thickness of the second sub-layer, the third sub-layer, and the fourth sub-layer is 200 nm, and the thickness ratio of the three is 2:1:2.

[0078] The fifth sub-layer is an Si-doped AlGaN layer with a thickness of 35 nm and an Si doping concentration of 3×10 18 cm -3 ; the proportion of its Al component is 0.1.

[0079] The sixth sub-layer includes alternately stacked Si-doped GaN layers and InGaN layers with 12 periods. The thickness of the Si-doped GaN layer is 10 nm and the Si doping concentration is 6.5×10 17 cm -3 ; the thickness of the InGaN layer is 4 nm and the proportion of In component is 0.1.

[0080] The rest are the same as in Example 1.

[0081] Example 6 This example provides a green Micro-LED epitaxial structure, which is different from that of Example 4 in that: The Si doping concentration of the third sub-layer is 8.5×10 18 cm -3 . The Si doping concentrations of the second and fourth sub-layers are 5.5×10 18 cm -3 .

[0082] The rest are the same as in Example 4.

[0083] Example 7 This example provides a green Micro-LED epitaxial structure, which is different from that of Example 4 in that: The Si doping concentration of the third sub-layer is 8.5×10 18 cm -3 . The Si doping concentrations of the second and fourth sub-layers are 5.5×10 18 cm -3 . The Si doping concentration of the fifth sub-layer is 6×10 18 cm -3 .

[0084] The rest are the same as in Example 4.

[0085] Example 8 This example provides a green Micro-LED epitaxial structure, which is different from that of Example 7 in that: In the fifth sub-layer, the proportion of Al component increases linearly from 0.05 to 0.15 along the growth direction of the epitaxial structure.

[0086] The rest are the same as in Example 7.

[0087] Comparative Example 1 This comparative example provides a green Micro-LED epitaxial structure, which is different from that of Example 1 in that: It does not include an electron transport layer, and the rest are the same as in Example 1.

[0088] Comparative Example 2 This comparative example provides a green Micro-LED epitaxial structure, which is different from that of Example 1 in that: The electron transport layer does not include the second sub-layer, the third sub-layer and the fourth sub-layer.

[0089] The rest are the same as those in Example 1.

[0090] Comparative Example 3 This comparative example provides a green Micro-LED epitaxial structure, which is different from that of Example 1 in that: The electron transport layer does not include the first sub-layer and the fifth sub-layer.

[0091] The rest are the same as those in Example 1.

[0092] Comparative Example 4 This comparative example provides a green Micro-LED epitaxial structure, which is different from that of Example 1 in that: The C doping concentration of the second sub-layer and the third sub-layer is 6×10 18 cm -3 , and the Si doping concentration is 5.5×10 18 cm -3 . The C doping concentration in the fourth sub-layer is 3×10 18 cm -3 , and the Si doping concentration is 1×10 18 cm -3 .

[0093] The rest are the same as those in Example 1.

[0094] Comparative Example 5 This comparative example provides a green Micro-LED epitaxial structure, which is different from that of Example 1 in that: The Si doping concentration of the first sub-layer is 6×10 18 cm -3 .

[0095] The C doping concentration of the second sub-layer and the third sub-layer is 2.5×10 17 cm -3 , and the Si doping concentration is 1.5×10 18 cm -3 . The C doping concentration of the fourth sub-layer is 3×10 17 cm -3 , and the Si doping concentration is 2.5×10 18 cm -3 .

[0096] The rest are the same as those in Example 1.

[0097] The epitaxial structures obtained in Examples 1 to 8 and Comparative Examples 1 to 5 were fabricated into Micro-LEDs with a size of 3 mil × 5 mil and a horizontal structure, and then tested as follows: (1) The luminous brightness was tested at a current density of 0.2 A / cm 2 , and the luminous brightness improvement rate was calculated based on the data of Comparative Example 1.

[0098] (2) Electrofluorescence tests were carried out at current densities of 0.2 A / cm 2 and 1 A / cm 2 to obtain the wavelengths at different current densities. The wavelength shift was calculated according to the following formula: Wavelength shift = |Test wavelength 1 (0.2 A / cm 2 ) - Test wavelength 2 (1 A / cm 2 )|.

[0099] The specific results are shown in the following table:

[0100] As can be seen from the table, by using the green Micro-LED epitaxial structure of the present invention, the luminous efficiency of Micro-LED can be greatly improved and its wavelength uniformity can be optimized.

[0101] The above is the preferred embodiment of the invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A green light Micro-LED epitaxial structure, characterized in that, It includes a substrate, a buffer layer, an undoped GaN layer, an N-type GaN layer, an electron transport layer, a multi-quantum well layer, and a P-type GaN layer that are sequentially stacked on the substrate; Among them, the electron transport layer includes a first sub-layer, a second sub-layer, a third sub-layer, a fourth sub-layer, a fifth sub-layer, and a sixth sub-layer that are sequentially stacked on the N-type GaN layer. The first sub-layer includes alternately stacked undoped Al-containing nitride layers and Si-doped Al-containing nitride layers; the second sub-layer, the third sub-layer, and the fourth sub-layer are all C, Si co-doped Ga-containing nitride layers; the fifth sub-layer is a Si-doped AlGaN layer, and the sixth sub-layer includes alternately stacked Si-doped GaN layers and InGaN layers; The Si doping concentrations of the second sub-layer, the third sub-layer, and the fourth sub-layer are all greater than the Si doping concentration of the Si-doped Al-containing nitride layer; the Si doping concentrations of the second sub-layer, the third sub-layer, and the fourth sub-layer are respectively greater than their C doping concentrations.

2. The green Micro-LED epitaxial structure according to claim 1, wherein The undoped Al-containing nitride layer is an undoped AlN layer, an undoped AlGaN layer, or an undoped AlInGaN layer; and / or The Si-doped Al-containing nitride layer is a Si-doped AlN layer, a Si-doped AlGaN layer, or a Si-doped AlInGaN layer; and / or The Ga-containing nitride layer is a GaN layer, an AlGaN layer, an AlInGaN layer, an InGaN layer, a BGaN layer, or a BInGaN layer.

3. The green light Micro-LED epitaxial structure according to claim 1, wherein The undoped Al-containing nitride layer is an undoped AlN layer, the Si-doped Al-containing nitride layer is a Si-doped AlGaN layer, and the Ga-containing nitride layer is a GaN layer; or The undoped Al-containing nitride layer is an undoped AlN layer, the Si-doped Al-containing nitride layer is a Si-doped AlInGaN layer, and the Ga-containing nitride layer is a BGaN layer.

4. The green light Micro-LED epitaxial structure according to claim 1, characterized in that, The undoped Al-containing nitride layer is an undoped AlGaN layer, the Si-doped Al-containing nitride layer is a Si-doped AlInGaN layer, and the Ga-containing nitride layer is an InGaN layer; or The undoped Al-containing nitride layer is an undoped AlGaN layer, the Si-doped Al-containing nitride layer is a Si-doped AlGaN layer, and the Ga-containing nitride layer is an AlGaN layer.

5. The green light Micro-LED epitaxial structure according to any one of claims 1 to 4, characterized in that, The thickness of the first sub-layer is 50 nm to 500 nm, and the thickness ratio of the undoped Al-containing nitride layer to the Si-doped Al-containing nitride layer is 1:2 to 1:5; the Si doping concentration of the Si-doped Al-containing nitride layer is 1×10 17 cm -3 ~1×10 18 cm -3 ; the number of periods of the first sub-layer is 1 to 10; and / or The total thickness of the second sub-layer, the third sub-layer, and the fourth sub-layer is 50 nm to 500 nm, and the thickness ratio of the second sub-layer, the third sub-layer, and the fourth sub-layer is 1:1:1 to 10:1:10; and / or The C doping concentration of the second sub-layer, the third sub-layer, and the fourth sub-layer is 1×10 17 cm -3 ~1×10 18 cm -3 , the Si doping concentration is 3×10 18 cm -3 ~1×10 19 cm -3 ; and / or The thickness of the fifth sub-layer is 10 nm to 100 nm, and its Si doping concentration is 3×10 18 cm -3 ~8×10 18 cm -3 , and the proportion of its Al component is 0.01 to 0.3; and / or The thickness of the Si-doped GaN layer is 5 nm to 20 nm, and its Si doping concentration is 1×10 17 cm -3 ~1×10 18 cm -3 ; and / or The thickness of the InGaN layer is 1 nm to 5 nm, and the proportion of its In component is 0.01 to 0.2; and / or The number of periods of the sixth sub-layer is 3 to 20.

6. The green light Micro-LED epitaxial structure according to any one of claims 1 to 4, characterized in that, The Si doping concentration of the third sub-layer > the Si doping concentration of the second sub-layer, and the Si doping concentration of the second sub-layer is the same as the Si doping concentration of the fourth sub-layer; and / or The C doping concentrations of the second sub-layer, the third sub-layer, and the fourth sub-layer are the same.

7. The green light Micro-LED epitaxial structure according to any one of claims 1 to 4, characterized in that, The Si doping concentration of the third sub-layer > the Si doping concentration of the fifth sub-layer > the Si doping concentration of the second sub-layer > the Si doping concentration of the first sub-layer, and the Si doping concentration of the second sub-layer is the same as the Si doping concentration of the fourth sub-layer.

8. The green light Micro-LED epitaxial structure according to any one of claims 1 to 4, characterized in that In the fifth sub-layer, the proportion of the Al component increases along the growth direction of the epitaxial structure.

9. A method for preparing a green Micro-LED epitaxial structure, which is used to prepare the green Micro-LED epitaxial structure according to any one of claims 1 to 8, characterized in that, Comprising: Providing a substrate, and sequentially growing a buffer layer, an undoped GaN layer, an N-type GaN layer, an electron transport layer, a multi-quantum well layer, and a P-type GaN layer on the substrate; Wherein, the electron transport layer includes a first sub-layer, a second sub-layer, a third sub-layer, a fourth sub-layer, a fifth sub-layer, and a sixth sub-layer sequentially stacked on the N-type GaN layer. The first sub-layer includes alternately stacked undoped Al-containing nitride layers and Si-doped Al-containing nitride layers; the second sub-layer, the third sub-layer, and the fourth sub-layer are all C and Si co-doped Ga-containing nitride layers; the fifth sub-layer is a Si-doped AlGaN layer, and the sixth sub-layer includes alternately stacked Si-doped GaN layers and InGaN layers; The Si doping concentrations of the second sub-layer, the third sub-layer, and the fourth sub-layer are all greater than the Si doping concentration of the Si-doped Al-containing nitride layer; the Si doping concentrations of the second sub-layer, the third sub-layer, and the fourth sub-layer are respectively greater than their C doping concentrations.

10. A green Micro-LED, characterized in that, Comprising the green Micro-LED epitaxial structure according to any one of claims 1 to 8.

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