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

Abstract

The present invention discloses a green light Micro-LED epitaxial structure and a preparation method thereof, and a green light Micro-LED, which relate to the field of semiconductor optoelectronic devices. The epitaxial structure sequentially 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; the electron transport layer sequentially includes a first sublayer, a second sublayer, a third sublayer, a fourth sublayer, a fifth sublayer, and a sixth sublayer, the first sublayer including an alternating stack of undoped Al-containing nitride layers and Si-doped Al-containing nitride layers; the second sublayer, the third sublayer, and the fourth sublayer are all Ga-containing nitride layers co-doped with C and Si, the fifth sublayer is a Si-doped AlGaN layer, and the sixth sublayer includes an alternating stack of Si-doped GaN layers and InGaN layers; the Si doping concentrations of the second sublayer, the third sublayer, and the fourth sublayer are all greater than the Si doping concentration of the Si-doped Al-containing nitride layer; and the Si doping concentrations of the second sublayer, the third sublayer, and the fourth sublayer are respectively greater than their C doping concentrations. Implementation of the present invention can improve light efficiency and wavelength uniformity.

Description

Technical Field

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

[0002] Micro-LED generally refers to chips with a size of less than 100μm. It has excellent performance and low power consumption. It is the latest and best application technology in the foreseeable multi-display scenario at the current stage. However, the operating current density of Micro-LED is generally 0.1~2A / cm 2 At such low current densities, achieving uniform current distribution and improving luminous efficiency become crucial issues. On the one hand, because the mobility of electrons in the GaN material system is much greater than that of holes, this leads to poor matching between electron and hole carriers in the multi-quantum well layers, resulting in low luminous efficiency. This is particularly true in green Micro-LED chips with high-In content quantum wells. The greater lattice mismatch between the quantum well layers and quantum barrier layers creates greater compressive stress, leading to even poorer recombination efficiency and lower luminous efficiency. On the other hand, because the resistivity of N-type GaN is higher than that of the transparent conductive layer (ITO) in the LED structure, it also hinders current spreading. Currently, one of the main approaches to addressing this electron-hole mismatch is to introduce a high barrier structure after the N-type GaN layer to reduce electron mobility. However, this structure often results in further deterioration of current distribution and reduced luminous uniformity. When used as a display screen, this can lead to significant pixel-to-pixel display variations and poor color consistency. Summary of the Invention

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

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

[0005] In order to solve the above problems, the present invention discloses a green light 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 stacked on the substrate in sequence;

[0006] The electron transport layer includes a first sublayer, a second sublayer, a third sublayer, a fourth sublayer, a fifth sublayer and a sixth sublayer sequentially stacked on the N-type GaN layer, wherein the first sublayer includes alternately stacked non-doped Al-containing nitride layers and Si-doped Al-containing nitride layers; the second sublayer, the third sublayer and the fourth sublayer are all Ga-containing nitride layers co-doped with C and Si; the fifth sublayer is a Si-doped AlGaN layer, and the sixth sublayer includes alternately stacked Si-doped GaN layers and InGaN layers;

[0007] The Si doping concentrations of the second sublayer, the third sublayer, and the fourth sublayer are all greater than the Si doping concentration of the Si-doped Al nitride layer; the Si doping concentrations in the second sublayer, the third sublayer, and the fourth sublayer are respectively greater than their C doping concentrations.

[0008] 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

[0009] 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

[0010] 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.

[0011] As an improvement of the above technical solution, the non-doped Al-containing nitride layer is a non-doped 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

[0012] The non-doped Al-containing nitride layer is a non-doped 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.

[0013] As an improvement of the above technical solution, the non-doped Al-containing nitride layer is a non-doped 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

[0014] The non-doped Al-containing nitride layer is a non-doped 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.

[0015] As an improvement to the above technical solution, the thickness of the first sub-layer is 50 nm to 500 nm, the thickness ratio of the non-doped 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 sublayer is 1 to 10; and / or

[0016] The total thickness of the second sublayer, the third sublayer, and the fourth sublayer is 50 nm to 500 nm, and the thickness ratio of the second sublayer, the third sublayer, and the fourth sublayer is 1:1:1 to 10:1:10; and / or

[0017] The C doping concentration of the second sublayer, the third sublayer, and the fourth sublayer is 1×10 17 cm -3 ~1×10 18 cm -3 , Si doping concentration is 3×10 18 cm -3 ~1×10 19 cm -3 and / or

[0018] The thickness of the fifth sublayer 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 Al component is 0.01~0.3; and / or

[0019] The thickness of the Si-doped GaN layer is 5 nm to 20 nm, and the Si doping concentration is 1×10 17 cm -3 ~1×10 18 cm -3 and / or

[0020] The thickness of the InGaN layer is 1 nm to 5 nm, and the proportion of In component is 0.01 to 0.2; and / or

[0021] The number of periods of the sixth sublayer is 3 to 20.

[0022] As an improvement to the above technical solution, the Si doping concentration of the third sublayer is greater than the Si doping concentration of the second sublayer, and the Si doping concentration of the second sublayer is the same as the Si doping concentration of the fourth sublayer; and / or

[0023] The second sublayer, the third sublayer, and the fourth sublayer have the same C doping concentration.

[0024] As an improvement of the above technical solution, the Si doping concentration of the third sublayer is greater than the Si doping concentration of the fifth sublayer and the Si doping concentration of the second sublayer is greater than the Si doping concentration of the first sublayer, and the Si doping concentration of the second sublayer is the same as the Si doping concentration of the fourth sublayer.

[0025] 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.

[0026] Correspondingly, the present invention also discloses a method for preparing a green light Micro-LED epitaxial structure, which is used to prepare the above-mentioned green light Micro-LED epitaxial structure, and comprises:

[0027] 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;

[0028] The electron transport layer includes a first sublayer, a second sublayer, a third sublayer, a fourth sublayer, a fifth sublayer and a sixth sublayer sequentially stacked on the N-type GaN layer, wherein the first sublayer includes alternately stacked non-doped Al-containing nitride layers and Si-doped Al-containing nitride layers; the second sublayer, the third sublayer and the fourth sublayer are all Ga-containing nitride layers co-doped with C and Si; the fifth sublayer is a Si-doped AlGaN layer, and the sixth sublayer includes alternately stacked Si-doped GaN layers and InGaN layers;

[0029] The Si doping concentrations of the second sublayer, the third sublayer, and the fourth sublayer are all greater than the Si doping concentration of the Si-doped Al nitride layer; the Si doping concentrations of the second sublayer, the third sublayer, and the fourth sublayer are respectively greater than their C doping concentrations.

[0030] Correspondingly, the present invention also discloses a green light Micro-LED, which includes the above-mentioned green light Micro-LED epitaxial structure.

[0031] The implementation of the present invention has the following beneficial effects:

[0032] In one embodiment of the present invention, a green Micro-LED epitaxial structure incorporates an electron transport layer between the N-type GaN layer and the multi-quantum well layer. The electron transport layer comprises a first, second, third, fourth, fifth, and sixth sublayers stacked sequentially on the N-type GaN layer. The first sublayer comprises alternating layers of undoped Al-containing nitride layers and Si-doped Al-containing nitride layers. The second, third, and fourth sublayers are all Ga-containing nitride layers co-doped with C and Si. The fifth sublayer is a Si-doped AlGaN layer, and the sixth sublayer comprises alternating layers of Si-doped GaN and InGaN layers. The Si doping concentrations in the second, third, and fourth sublayers are greater than that in the Si-doped Al-containing nitride layer. The introduction of Al into the first and fifth sublayers creates a high barrier, slowing the mobility of electron carriers and increasing the radiative recombination efficiency of electron and hole carriers in the multi-quantum well layer, thereby improving luminous efficiency. However, the introduction of Al will also weaken the uniformity of current distribution. For this reason, this embodiment also introduces C and Si co-doped Ga nitride layers as the second, third, and fourth sublayers, and controls the C doping concentration to be less than the Si doping concentration. Low-concentration C doping can lower the Fermi level, promote Si incorporation efficiency, and thus reduce the overall resistivity and optimize current distribution. C doping can also promote edge dislocation climb. C and Si co-doping can promote the formation of V-shaped pits, allowing hole carriers to enter deeper quantum well layers through the sidewalls of the V-shaped pits, not only improving the radiative recombination efficiency but also optimizing the current distribution. Even with the introduction of the first and fourth sublayers, the current spreading performance is still excellent, improving luminescence uniformity. In the sixth sublayer, Si-doped GaN layers and InGaN layers are used to alternately form a barrier / potential well structure, further optimizing electron distribution, facilitating stress release, reducing the polarization effect of the subsequently grown multi-quantum well layer, and improving luminescence efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the green light Micro-LED epitaxial structure in one embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is described in further detail below.

[0035] See also Figure 1 An embodiment of the present invention discloses a green light 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 stacked in sequence on the substrate 100.

[0036] The electron transport layer 500 includes a first sublayer 510, a second sublayer 520, a third sublayer 530, a fourth sublayer 540, a fifth sublayer 550 and a sixth sublayer 560 sequentially stacked on the N-type GaN layer 400. The first sublayer 510 includes an alternately stacked non-doped Al-containing nitride layer 511 and a Si-doped Al-containing nitride layer 512; the second sublayer 520, the third sublayer 530 and the fourth sublayer 540 are all C- and Si-co-doped G-containing layers. a nitride layer; the fifth sublayer 550 is a Si-doped AlGaN layer; the sixth sublayer 560 includes alternating Si-doped GaN layers 561 and InGaN layers 562; the Si doping concentrations of the second sublayer 520, the third sublayer 530, and the fourth sublayer 540 are all greater than the Si doping concentration of the Si-doped Al-containing nitride layer 512; and the Si doping concentrations of the second sublayer 520, the third sublayer 530, and the fourth sublayer 540 are all greater than their C doping concentrations. Specifically, Al is introduced into both the first sublayer 510 and the fifth sublayer 550, resulting in a high potential barrier that slows the mobility of electron carriers, increases the radiative recombination efficiency of electron and hole carriers in the multi-quantum well layer 600, and thus improves luminous efficiency. However, the introduction of Al can also weaken the uniformity of current distribution. To this end, this embodiment also introduces C and Si co-doped Ga nitride layers as the second sublayer 520, third sublayer 530, and fourth sublayer 540, with the C doping concentration controlled to be lower than the Si doping concentration. The low concentration of C doping can lower the Fermi level, promote the efficiency of Si incorporation, and thus reduce the overall resistivity and optimize the current distribution. C doping can also promote edge dislocation climb. C and Si co-doping can promote the formation of V-shaped pits, allowing hole carriers to enter deeper quantum well layers via the sidewalls of the V-shaped pits, not only improving the radiative recombination efficiency but also optimizing the current distribution. Even with the introduction of the first sublayer 510 and the fourth sublayer 540, the current spreading performance is still excellent. The alternating barrier / potential well structure formed by the Si-doped GaN layer 561 and the InGaN layer 562 in the sixth sublayer 560 further optimizes electron distribution and facilitates stress relief, reducing the polarization effect of the subsequently grown multi-quantum well layer 600 and improving luminous efficiency.

[0037] 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. Such an undoped Al-containing nitride layer 511 has a higher potential barrier, which helps further reduce the mobility of electron carriers.

[0038] Specifically, in some embodiments, the Si-doped Al nitride layer 512 is a Si-doped AlN layer, a Si-doped AlGaN layer, or a Si-doped AlInGaN layer, but is not limited thereto. Preferably, the Si-doped Al nitride layer 512 is an undoped AlN layer or an undoped AlGaN layer. Such a Si-doped Al nitride layer 512 has a higher potential barrier, which helps further reduce the mobility of electron carriers.

[0039] 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. Based on these Ga-containing nitride layers, current distribution can be optimized.

[0040] Preferably, after extensive research, it has been found that the following four combinations have better luminous efficiency and better current expansion performance:

[0041] (1) The undoped Al-containing nitride layer 511 is an undoped AlN layer, the Si-doped Al-containing nitride layer 512 is a Si-doped AlGaN layer, and the Ga-containing nitride layer is a GaN layer. In this embodiment, the proportion of Al in the Si-doped AlGaN layer is ≤ 0.2, and preferably, the proportion of Al in the Si-doped AlGaN layer is 0.05-0.15.

[0042] (2) The undoped Al-containing nitride layer 511 is an undoped AlN layer, the Si-doped Al-containing nitride layer 512 is a 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 is ≥0.2, the proportion of the In component is ≤0.1; and the proportion of the B component in the Ga-containing nitride layer (BGaN layer) is ≤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.

[0043] (3) The non-doped Al-containing nitride layer 511 is a non-doped 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 non-doped AlGaN layer is ≥0.1, the proportion of the Al component in the Si-doped AlInGaN layer is ≥0.1, and the proportion of the In component is ≤0.15; and the proportion of the In component in the Ga-containing nitride layer (InGaN layer) is ≤0.15. More preferably, the proportion of the Al component in the non-doped 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.

[0044] (4) The non-doped Al-containing nitride layer 511 is a non-doped 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 Al components in the non-doped AlGaN layer is ≥0.1, the proportion of Al components in the Si-doped AlGaN layer is ≥0.1; and the proportion of Al components in the Ga-containing nitride layer (AlGaN layer) is ≤0.08. More preferably, the proportion of Al components in the non-doped AlGaN layer is 0.1-0.15, the proportion of Al components in the Si-doped AlGaN layer is 0.1-0.15, and the proportion of Al components in the Ga-containing nitride layer (AlGaN layer) is 0.02-0.08.

[0045] Specifically, in some embodiments, the thickness of the first sub-layer 510 is 50 nm to 500 nm, and the number of periods thereof is 1 to 10. Preferably, the thickness of the first sub-layer 510 is 100 nm to 500 nm, and the number of periods thereof is 3 to 8.

[0046] Specifically, in some embodiments, the thickness ratio of the non-doped Al-containing nitride layer 511 to the Si-doped Al-containing nitride layer 512 is 1:2 to 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 non-doped Al-containing nitride layer 511 to the Si-doped Al-containing nitride layer 512 is 1:3 to 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 .

[0047] Specifically, in some embodiments, the total thickness of the second sublayer 520, the third sublayer 530, and the fourth sublayer 540 is 50 nm to 500 nm, wherein the thickness ratio of the second sublayer 520, the third sublayer 530, and the fourth sublayer 540 is (1-10):1:(1-10). Preferably, the total thickness of the second sublayer 520, the third sublayer 530, and the fourth sublayer 540 is 80 nm to 200 nm, wherein the thickness ratio of the second sublayer 520, the third sublayer 530, and the fourth sublayer 540 is (1-5):1:(5-8).

[0048] Specifically, in some embodiments, the second sublayer 520, the third sublayer 530, and the fourth sublayer 540 may have the same or different C doping concentrations and the same or different Si doping concentrations. However, the C doping concentration must be lower than the Si doping concentration. If the C doping concentration is higher than the Si doping concentration, the C may form donor doping, which in turn increases the resistivity and makes the current distribution more concentrated. Specifically, the Si doping concentration of the second sublayer 520 is greater than its C doping concentration, the Si doping concentration of the third sublayer 530 is greater than its C doping concentration, and the Si doping concentration of the fourth sublayer 540 is greater than its C doping concentration.

[0049] More specifically, in some embodiments, the C doping concentration of the second sub-layer 520, the third sub-layer 530, and the fourth sub-layer 540 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 Preferably, the C doping concentration of the second sub-layer 520, the third sub-layer 530, and the fourth sub-layer 540 is 1.5×10 17 cm -3 ~5×10 17 cm -3 , the Si doping concentration is 3×10 18 cm -3 ~9×10 18 cm -3 It should be noted that the C doping concentrations of the second sublayer 520 , the third sublayer 530 , and the fourth sublayer 540 are the same or different, and the Si doping concentrations of the second sublayer 520 , the third sublayer 530 , and the fourth sublayer 540 are the same or different.

[0050] Specifically, in some embodiments, the thickness of the fifth sublayer 550 is 10 nm to 100 nm, and the Si doping concentration is 3×10 18 cm -3 ~8×10 18 cm-3 The proportion of Al component is 0.01~0.3. Preferably, the thickness of the fifth sublayer 550 is 20nm~50nm, and the Si doping concentration is 5×10 18 cm -3 ~8×10 18 cm -3 ; The proportion of Al component is 0.05~0.2.

[0051] Specifically, in some embodiments, the period number 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 the 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 In component is 0.01 to 0.2. Preferably, the number of periods of the sixth sublayer 560 is 5 to 15. The thickness of the Si-doped GaN layer 561 is 5 nm to 15 nm, and the Si doping concentration is 1×10 17 cm -3 ~5×10 17 cm -3 ; The thickness of the InGaN layer 562 is 2nm~5nm, and the proportion of In component is 0.05~0.12.

[0052] Specifically, the substrate 100 is a sapphire substrate or a silicon substrate, but is not limited thereto.

[0053] Specifically, the buffer layer 200 is an AlN layer or an AlGaN layer, but is not limited thereto. The buffer layer 200 has a thickness of 30 nm to 80 nm.

[0054] Specifically, the thickness of the undoped GaN layer 300 is 1 μm to 3 μm.

[0055] Specifically, the doping element of the N-type GaN layer 400 is Si, but not limited thereto. The doping concentration of Si in the N-type GaN layer 400 is 1×10 18 cm -3 ~5×10 19 cm -3 , its thickness is 1μm~3μm.

[0056] Specifically, the multi-quantum well layer 600 includes alternately stacked InGaN quantum well layers and GaN quantum barrier layers, with a period number of 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.

[0057] Specifically, the doping element of the P-type GaN layer 700 is Mg, but 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 , its thickness is 20nm~200nm.

[0058] Preferably, in some embodiments of the present invention, the Si doping concentration of the third sublayer 530 is greater than that of the second sublayer 520, the Si doping concentration of the second sublayer 520 is the same as that of the fourth sublayer 540; and the C doping concentrations of the second, third, and fourth sublayers 520, 530, and 540 are the same. By controlling the relationship between the Si doping concentrations of the second, third, and fourth sublayers 520, 530, and 540, the distribution of electrons can be effectively adjusted, current congestion can be avoided, and luminous uniformity and luminous efficiency can be improved. By controlling the C doping concentration, the distribution of the V-shaped pits is optimized, further promoting the uniformity of current distribution.

[0059] More preferably, the Si doping concentration of the third sublayer 530 is greater than the Si doping concentration of the fifth sublayer 550 , the Si doping concentration of the second sublayer 520 is greater than the Si doping concentration of the first sublayer 510 , and the Si doping concentration of the second sublayer 520 is the same as the Si doping concentration of the fourth sublayer 540 .

[0060] Preferably, in some embodiments of the present invention, the Al content in the fifth sublayer 550 increases gradually, more preferably linearly, along the epitaxial growth direction. This approach improves the crystal quality of the fifth sublayer 550, further slowing the flow of electron carriers; it also effectively optimizes the uniform distribution of electron carriers.

[0061] Accordingly, the present invention also provides a method for preparing a green light Micro-LED epitaxial structure, which is used to prepare the above-mentioned green light Micro-LED epitaxial structure, and specifically comprises the following steps:

[0062] S1: providing a substrate;

[0063] S2: 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;

[0064] Specifically, the electron transport layer includes a first sublayer, a second sublayer, a third sublayer, a fourth sublayer, a fifth sublayer, and a sixth sublayer sequentially stacked on an N-type GaN layer. The first sublayer includes alternating layers of undoped Al-containing nitride layers and Si-doped Al-containing nitride layers; the second, third, and fourth sublayers are all Ga-containing nitride layers co-doped with C and Si; the fifth sublayer is a Si-doped AlGaN layer, and the sixth sublayer includes alternating layers of Si-doped GaN and InGaN layers. The electron transport layer in the present invention can reduce the transmission speed of electron carriers, optimize their distribution, and promote hole injection into deeper multi-quantum well layers. This not only effectively improves luminous efficiency, but also ensures current spread uniformity and enhances luminous uniformity.

[0065] Specifically, in some embodiments of the present invention, step S2 includes:

[0066] S21: growing a buffer layer on the substrate;

[0067] Specifically, in some embodiments, an AlN layer is grown by PVD to serve as a buffer layer.

[0068] S22: growing a non-doped GaN layer on the buffer layer;

[0069] Specifically, in some embodiments, the undoped GaN layer is grown by MOCVD at a growth temperature of 1000° C. to 1200° C. and a growth pressure of 100 torr to 500 torr.

[0070] S23: growing an N-type GaN layer on the undoped GaN layer;

[0071] Specifically, in some embodiments, the N-type GaN layer is grown by MOCVD at a growth temperature of 1100° C. to 1200° C. and a growth pressure of 100 torr to 500 torr.

[0072] S24: growing an electron transport layer on the N-type GaN layer;

[0073] Specifically, in some embodiments, the electron transport layer can be obtained by sequentially growing the first sublayer, the second sublayer, the third sublayer, the fourth sublayer, the fifth sublayer and the sixth sublayer by MOCVD.

[0074] The first sublayer is grown at a temperature of 1000°C to 1200°C and a pressure of 50 torr to 300 torr. The second, third, and fourth sublayers are grown at a temperature of 800°C to 1200°C and a pressure of 50 torr to 500 torr. The fifth sublayer is grown at a temperature of 800°C to 1000°C and a pressure of 50 torr to 300 torr. The sixth sublayer is grown at a pressure of 800°C to 900°C and a pressure of 50 torr to 500 torr.

[0075] S25: growing a multi-quantum well layer on the electron transport layer;

[0076] Specifically, in some embodiments, InGaN quantum well layers and GaN quantum barrier layers are periodically grown on the electron transport layer by MOCVD until a multi-quantum well layer is obtained.

[0077] The InGaN quantum well layer is grown at a temperature of 730°C to 800°C and a pressure of 100 torr to 300 torr. The GaN quantum barrier layer is grown at a temperature of 850°C to 1000°C and a pressure of 100 torr to 300 torr.

[0078] S25: growing a P-type GaN layer on the multi-quantum well layer;

[0079] Specifically, in one embodiment of the present invention, the P-type GaN layer is grown by MOCVD, with a growth temperature of 950° C. to 1000° C. and a growth pressure of 100 torr to 300 torr.

[0080] The present invention will be further described below with specific embodiments:

[0081] Example 1

[0082] This embodiment provides a green light 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 stacked in sequence on the substrate.

[0083] 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 3μm.

[0084] The electron transport layer includes a first sublayer, a second sublayer, a third sublayer, a fourth sublayer, a fifth sublayer and a sixth sublayer sequentially stacked on the N-type GaN layer.

[0085] The first sublayer comprises alternately stacked undoped Al0.3 Ga 0.7 N layer and Si doped with Al 0.5 In 0.05 Ga 0.45 N layer, with a period number of 5. The thickness of the first sublayer is 100nm, non-doped Al 0.3 Ga 0.7 N layer and Si doped with Al 0.5 In 0.05 Ga 0.45 The thickness ratio of the N layer is 1:4. Si doped with Al 0.5 In 0.05 Ga 0.45 The doping concentration of the N layer is 5×10 17 cm -3 .

[0086] The second sublayer is a C and Si co-doped GaN layer, and its C doping concentration is 2.5×10 17 cm -3 , Si doping concentration is 5.5×10 18 cm -3 The third sublayer is a C and Si co-doped GaN layer with a C doping concentration of 2.5×10 17 cm -3 , Si doping concentration is 5.5×10 18 cm -3 The fourth sublayer is C and Si co-doped Al 0.05 Ga 0.95 The C doping concentration of the N layer is 3×10 17 cm -3 , Si doping concentration is 5.5×10 18 cm -3 The total thickness of the second sublayer, the third sublayer, and the fourth sublayer is 200 nm, and the thickness ratio of the three is 2:1:2.

[0087] The fifth sublayer 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 Al component is 0.1.

[0088] The sixth sublayer includes alternately stacked Si-doped GaN layers and InGaN layers, with a period 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 4nm, and the proportion of In component is 0.1.

[0089] The multi-quantum well layer includes alternating InGaN quantum well layers and GaN quantum barrier layers, with a period of 10. The InGaN quantum well layer has an In component ratio of 0.3 and a thickness of 3 nm. The GaN quantum barrier layer has a thickness of 10 nm.

[0090] Among them, the Mg doping concentration in the P-type GaN layer is 8×10 19 cm -3 , and its thickness is 100nm.

[0091] Example 2

[0092] This embodiment provides a green light Micro-LED epitaxial structure, which differs from the first embodiment in that the electron transport layer is different. The details are as follows:

[0093] The first sublayer includes alternately stacked non-doped AlN layers and Si-doped Al 0.12 Ga 0.88 N layer, the period number is 4. The thickness of the first sub-layer is 80nm, the non-doped AlN layer and the Si doped Al 0.12 Ga 0.88 The thickness ratio of the N layer is 1:3. Si doped with Al 0.12 Ga 0.88 The doping concentration of the N layer is 8.5×10 17 cm -3 .

[0094] The second, third, and fourth sublayers are all C and Si co-doped GaN layers, with a C doping concentration of 2.5×10 17 cm -3 , Si doping concentration is 5.5×10 18 cm -3 The total thickness of the second sublayer, the third sublayer, and the fourth sublayer is 200 nm, and the thickness ratio of the three is 2:1:2.

[0095] The fifth sublayer 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 Al component is 0.1.

[0096] The sixth sublayer includes alternately stacked Si-doped GaN layers and InGaN layers, with a period 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 4nm, and the proportion of In component is 0.1.

[0097] The rest are the same as in Example 1.

[0098] Example 3

[0099] This embodiment provides a green light Micro-LED epitaxial structure, which differs from the first embodiment in that the electron transport layer is different. The details are as follows:

[0100] The first sublayer includes alternately stacked non-doped AlN layers and Si-doped Al 0.35 In 0.08 Ga 0.57 N layer, the period number is 4. The thickness of the first sub-layer is 80nm, the non-doped AlN layer and the Si doped Al 0.35 In 0.08 Ga 0.57 The thickness ratio of the N layer is 1:3. Si doped with Al 0.35 In 0.08 Ga 0.57 The doping concentration of the N layer is 8×10 17 cm -3 .

[0101] The second, third and fourth sublayers are all C and Si co-doped BGaN layers, with a C doping concentration of 3×10 17 cm -3 , Si doping concentration is 8.5×10 18 cm -3 The total thickness of the second sublayer, the third sublayer, and the fourth sublayer is 200 nm, and the thickness ratio of the three is 2:1:2.

[0102] The fifth sublayer 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 Al component is 0.1.

[0103] The sixth sublayer includes alternately stacked Si-doped GaN layers and InGaN layers, with a period 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 4nm, and the proportion of In component is 0.1.

[0104] The rest are the same as in Example 1.

[0105] Example 4

[0106] This embodiment provides a green light Micro-LED epitaxial structure, which differs from the first embodiment in that the electron transport layer is different. The details are as follows:

[0107] The first sublayer comprises alternately stacked undoped Al 0.12 Ga 0.88 N layer and Si doped with Al 0.15In 0.1 Ga 0.75 N layer, the period number is 4. The thickness of the first sub-layer is 80nm, non-doped Al 0.12 Ga 0.88 N layer and Si doped with Al 0.15 In 0.1 Ga 0.75 The thickness ratio of the N layer is 1:3. Si doped with Al 0.15 In 0.1 Ga 0.75 The doping concentration of the N layer is 7×10 17 cm -3 .

[0108] The second, third and fourth sublayers are all C and Si co-doped with In 0.11 Ga 0.89 The C doping concentration of the N layer is 2×10 17 cm -3 , Si doping concentration is 7×10 18 cm -3 The total thickness of the second sublayer, the third sublayer, and the fourth sublayer is 200 nm, and the thickness ratio of the three is 2:1:2.

[0109] The fifth sublayer 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 Al component is 0.1.

[0110] The sixth sublayer includes alternately stacked Si-doped GaN layers and InGaN layers, with a period 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 4nm, and the proportion of In component is 0.1.

[0111] The rest are the same as in Example 1.

[0112] Example 5

[0113] This embodiment provides a green light Micro-LED epitaxial structure, which differs from the first embodiment in that the electron transport layer is different. The details are as follows:

[0114] The first sublayer comprises alternately stacked undoped Al 0.12 Ga 0.88 N layer and Si doped with Al 0.15 Ga 0.85 N layer, the period number is 4. The thickness of the first sub-layer is 80nm, non-doped Al 0.12 Ga 0.88 N layer and Si doped with Al0.15 Ga 0.85 The thickness ratio of the N layer is 1:3. Si doped with Al 0.15 Ga 0.85 The doping concentration of the N layer is 5×10 17 cm -3 .

[0115] The second, third and fourth sublayers are all C and Si co-doped Al 0.06 Ga 0.94 The C doping concentration of the N layer is 2×10 17 cm -3 , Si doping concentration is 8×10 18 cm -3 The total thickness of the second sublayer, the third sublayer, and the fourth sublayer is 200 nm, and the thickness ratio of the three is 2:1:2.

[0116] The fifth sublayer 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 Al component is 0.1.

[0117] The sixth sublayer includes alternately stacked Si-doped GaN layers and InGaN layers, with a period 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 4nm, and the proportion of In component is 0.1.

[0118] The rest are the same as in Example 1.

[0119] Example 6

[0120] This embodiment provides a green Micro-LED epitaxial structure, which differs from Embodiment 4 in that:

[0121] The Si doping concentration of the third sublayer is 8.5×10 18 cm -3 The Si doping concentration of the second and fourth sublayers is 5.5×10 18 cm -3 .

[0122] The rest are the same as in Example 4.

[0123] Example 7

[0124] This embodiment provides a green Micro-LED epitaxial structure, which differs from Embodiment 4 in that:

[0125] The Si doping concentration of the third sublayer is 8.5×10 18 cm-3 The Si doping concentration of the second and fourth sublayers is 5.5×10 18 cm -3 The doping concentration of the fifth sublayer Si is 6×10 18 cm -3 .

[0126] The rest are the same as in Example 4.

[0127] Example 8

[0128] This embodiment provides a green Micro-LED epitaxial structure, which differs from Embodiment 7 in that:

[0129] In the fifth sublayer, the proportion of Al components increases linearly from 0.05 to 0.15 along the growth direction of the epitaxial structure.

[0130] The rest are the same as in Example 7.

[0131] Comparative Example 1

[0132] This comparative example provides a green light Micro-LED epitaxial structure, which differs from Example 1 in that:

[0133] The electron transport layer is not included, and the rest is the same as in Example 1.

[0134] Comparative Example 2

[0135] This comparative example provides a green light Micro-LED epitaxial structure, which differs from Example 1 in that:

[0136] The second sublayer, the third sublayer and the fourth sublayer are not included in the electron transport layer.

[0137] The rest are the same as in Example 1.

[0138] Comparative Example 3

[0139] This comparative example provides a green light Micro-LED epitaxial structure, which differs from Example 1 in that:

[0140] The first sublayer and the fifth sublayer are not included in the electron transport layer.

[0141] The rest are the same as in Example 1.

[0142] Comparative Example 4

[0143] This comparative example provides a green light Micro-LED epitaxial structure, which differs from Example 1 in that:

[0144] The C doping concentration of the second and third sublayers is 6×10 18 cm -3, Si doping concentration is 5.5×10 18 cm -3 The C doping concentration in the fourth sublayer is 3×10 18 cm -3 , the Si doping concentration is 1×10 18 cm -3 .

[0145] The rest are the same as in Example 1.

[0146] Comparative Example 5

[0147] This comparative example provides a green light Micro-LED epitaxial structure, which differs from Example 1 in that:

[0148] The Si doping concentration of the first sublayer is 6×10 18 cm -3 .

[0149] The C doping concentration of the second and third sublayers is 2.5×10 17 cm -3 , Si doping concentration is 1.5×10 18 cm -3 The C doping concentration of the fourth sublayer is 3×10 17 cm -3 , Si doping concentration is 2.5×10 18 cm -3 .

[0150] The rest are the same as in Example 1.

[0151] The epitaxial structures obtained in Examples 1 to 8 and Comparative Examples 1 to 5 were prepared into 3 mil × 5 mil Micro-LEDs with a horizontal structure, and then tested as follows;

[0152] (1) At 0.2A / cm 2 The luminous brightness was tested at a current density of , and the luminous brightness improvement rate was calculated based on the data of comparative example 1.

[0153] (2) Conduct electroluminescence test with a current density of 0.2A / cm 2 and 1A / cm 2 , the wavelength under different current densities is obtained, and the wavelength shift is calculated according to the following formula:

[0154] Wavelength shift = |Test wavelength 1 (0.2A / cm 2 )-Test wavelength 2 (1A / cm 2 )|.

[0155] The specific results are shown in the following table:

[0156]

[0157] As can be seen from the table, the use of the green light Micro-LED epitaxial structure in the present invention can greatly improve the luminous efficiency of Micro-LED and optimize its wavelength uniformity.

[0158] The above is a preferred embodiment of the invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A green light Micro-LED epitaxial structure, characterized in that: The method comprises 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 sequentially stacked on the substrate; The electron transport layer includes a first sublayer, a second sublayer, a third sublayer, a fourth sublayer, a fifth sublayer and a sixth sublayer sequentially stacked on the N-type GaN layer, wherein the first sublayer includes alternately stacked non-doped Al-containing nitride layers and Si-doped Al-containing nitride layers; the second sublayer, the third sublayer and the fourth sublayer are all Ga-containing nitride layers co-doped with C and Si; the fifth sublayer is a Si-doped AlGaN layer, and the sixth sublayer includes alternately stacked Si-doped GaN layers and InGaN layers; The Si doping concentrations of the second sublayer, the third sublayer, and the fourth sublayer are all greater than the Si doping concentration of the Si-doped Al nitride layer; the Si doping concentrations of the second sublayer, the third sublayer, and the fourth sublayer are respectively greater than their C doping concentrations; The undoped Al-containing nitride layer is an undoped AlN layer, an undoped AlGaN layer or an undoped AlInGaN layer; The Si-doped Al-containing nitride layer is a Si-doped AlN layer, a Si-doped AlGaN layer or a Si-doped AlInGaN layer; 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.

2. The green Micro-LED epitaxial structure according to claim 1, wherein: The non-doped Al-containing nitride layer is a non-doped 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 non-doped Al-containing nitride layer is a non-doped 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.

3. The green Micro-LED epitaxial structure according to claim 1, wherein: The non-doped Al-containing nitride layer is a non-doped 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 non-doped Al-containing nitride layer is a non-doped 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.

4. The green Micro-LED epitaxial structure according to any one of claims 1 to 3, wherein: The thickness of the first sublayer is 50 nm to 500 nm, the thickness ratio of the non-doped 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 sublayer is 1 to 10; and / or The total thickness of the second sublayer, the third sublayer, and the fourth sublayer is 50 nm to 500 nm, and the thickness ratio of the second sublayer, the third sublayer, and the fourth sublayer is 1:1:1 to 10:1:10; and / or The C doping concentration of the second sublayer, the third sublayer, and the fourth sublayer is 1×10 17 cm -3 ~1×10 18 cm -3 , Si doping concentration is 3×10 18 cm -3 ~1×10 19 cm -3 and / or The thickness of the fifth sublayer 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 Al component is 0.01~0.3; and / or The thickness of the Si-doped GaN layer is 5 nm to 20 nm, and the 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 In component is 0.01 to 0.2; and / or The number of periods of the sixth sublayer is 3 to 20.

5. The green Micro-LED epitaxial structure according to any one of claims 1 to 3, wherein: The Si doping concentration of the third sub-layer is greater than 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 second sublayer, the third sublayer, and the fourth sublayer have the same C doping concentration.

6. The green Micro-LED epitaxial structure according to any one of claims 1 to 3, wherein: The Si doping concentration of the third sublayer is greater than the Si doping concentration of the fifth sublayer and greater than the Si doping concentration of the second sublayer and greater than the Si doping concentration of the first sublayer. The Si doping concentration of the second sublayer is the same as the Si doping concentration of the fourth sublayer.

7. The green Micro-LED epitaxial structure according to any one of claims 1 to 3, wherein: In the fifth sub-layer, the proportion of the Al component increases along the growth direction of the epitaxial structure.

8. A method for preparing a green light Micro-LED epitaxial structure, for preparing the green light Micro-LED epitaxial structure according to any one of claims 1 to 7, characterized in that: include: 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; The electron transport layer includes a first sublayer, a second sublayer, a third sublayer, a fourth sublayer, a fifth sublayer and a sixth sublayer sequentially stacked on the N-type GaN layer, the first sublayer includes alternately stacked non-doped Al-containing nitride layers and Si-doped Al-containing nitride layers; the second sublayer, the third sublayer and the fourth sublayer are all Ga-containing nitride layers co-doped with C and Si; the fifth sublayer is a Si-doped AlGaN layer, and the sixth sublayer includes alternately stacked Si-doped GaN layers and InGaN layers; The Si doping concentrations of the second sublayer, the third sublayer, and the fourth sublayer are all greater than the Si doping concentration of the Si-doped Al nitride layer; the Si doping concentrations of the second sublayer, the third sublayer, and the fourth sublayer are respectively greater than their C doping concentrations.

9. A green light Micro-LED, characterized in that: It comprises the green light Micro-LED epitaxial structure as described in any one of claims 1 to 7.

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