GaN-based light-emitting diode epitaxial wafer and preparation method thereof, and light-emitting diode

Abstract

The present invention provides a GaN-based light-emitting diode epitaxial wafer and a preparation method thereof, and a light-emitting diode. The GaN-based light-emitting diode epitaxial wafer includes a multi-quantum well layer, and the multi-quantum well layer is a periodic structure in which a quantum well layer and a quantum barrier layer grow alternately; wherein the last quantum barrier layer grown is a composite quantum barrier layer, and the composite quantum barrier layer includes an InN sublayer, an InAlGaN sublayer, and an AlN sublayer grown in sequence, and the In component of the InAlGaN sublayer gradually decreases along the epitaxial growth direction, and the Al component of the InAlGaN sublayer gradually increases along the epitaxial growth direction. The present invention improves the lattice matching of the quantum well layer and the P layer, and the energy level gradually transitions, effectively reducing the potential barrier peak formed by the quantum well and the valence band of the electron blocking layer, which is conducive to the injection of holes, and at the same time plays the role of a partial electron blocking layer, reduces electron overflow, improves the luminous efficiency of the light-emitting diode, and is also conducive to the improvement of its antistatic ability.

Description

Technical Field

[0001] The invention relates to the technical field of GaN-based light-emitting diodes, and in particular to a GaN-based light-emitting diode epitaxial wafer and a preparation method thereof, and a light-emitting diode. Background Art

[0002] At present, GaN-based light emitting diodes (LEDs) have been widely used in solid-state lighting and display fields due to their high efficiency, energy saving, and environmental protection. As the core area of ​​GaN-based light emitting diodes, multi-quantum well structures have also been widely studied.

[0003] Among them, the multi-quantum well structure is generally composed of InGaN quantum well layers and GaN quantum barrier layers stacked alternately. The traditional last quantum barrier layer is a GaN layer that repeats the previous quantum barrier layer. It will produce a large lattice mismatch and energy band change with the EBL electron barrier layer. The sudden change of the energy band will form a potential barrier peak in the last quantum barrier layer, which is not conducive to the injection of holes and affects the luminescence efficiency. Summary of the invention

[0004] Based on this, the purpose of the present invention is to provide a GaN-based light-emitting diode epitaxial wafer and a preparation method thereof, and a light-emitting diode, aiming to solve at least one technical problem in the background technology.

[0005] A GaN-based light-emitting diode epitaxial wafer according to an embodiment of the present invention comprises a multi-quantum well layer, wherein the multi-quantum well layer is a periodic structure in which quantum well layers and quantum barrier layers are alternately grown;

[0006] Among them, the last quantum barrier layer grown is a composite quantum barrier layer, which includes an InN sublayer, an InAlGaN sublayer and an AlN sublayer grown in sequence, the In component of the InAlGaN sublayer gradually decreases along the epitaxial growth direction, and the Al component of the InAlGaN sublayer gradually increases along the epitaxial growth direction.

[0007] Preferably, the growth temperature of the AlN sublayer is higher than the growth temperature of the InN sublayer, and the growth temperature of the InAlGaN sublayer increases gradually.

[0008] Preferably, the growth temperature of the InAlGaN sublayer gradually increases from the growth temperature of the InN sublayer to the growth temperature of the AlN sublayer, the growth temperature of the InN sublayer is 820-860°C, and the growth temperature of the AlN sublayer is 870-920°C.

[0009] Preferably, the In component of the InAlGaN sublayer gradually decreases from a first component value to 0 along the epitaxial growth direction;

[0010] The Al component of the InAlGaN sublayer gradually increases from 0 to a second component value along the epitaxial growth direction;

[0011] Among them, the first component value is 0.1-0.2, and the second component value is 0.1-0.3.

[0012] Preferably, the In component of the InN sublayer is less than or equal to the first component value, and the Al component of the AlN sublayer is 0.2-0.5.

[0013] Preferably, the thickness of the composite quantum barrier layer is 8-15 nm, wherein the thickness of the InN sublayer is 0.5-3 nm, the thickness of the InAlGaN sublayer is 5-10 nm, and the thickness of the AlN sublayer is 0.5-3 nm.

[0014] Preferably, it also includes a substrate, a GaN low-temperature buffer layer, an undoped GaN layer, an N-type doped GaN layer, an electron blocking layer and a p-type doped GaN layer;

[0015] The GaN low-temperature buffer layer, the undoped GaN layer, the N-type doped GaN layer, the multi-quantum well layer, the electron blocking layer and the p-type doped GaN layer are epitaxially grown in sequence on the substrate.

[0016] According to an embodiment of the present invention, a method for preparing a GaN-based light-emitting diode epitaxial wafer is used to prepare the above-mentioned GaN-based light-emitting diode epitaxial wafer. The preparation method comprises:

[0017] Alternately grow quantum well layers and quantum barrier layers to prepare multiple quantum well layers. When growing the last quantum barrier layer:

[0018] First, the In source is introduced to grow the InN sublayer, and then the Ga source and Al source are introduced, and the In source is continued to be introduced, while the In source input is controlled to gradually decrease and the Al source input is gradually increased to grow an InAlGaN sublayer with gradual changes in Al and In components. Finally, the Ga source and In source are turned off, and the Al source is kept introduced to grow the AlN sublayer.

[0019] Preferably, before the step of alternately growing quantum well layers and quantum barrier layers to prepare a multi-quantum well layer, the method further comprises:

[0020] Providing a substrate for epitaxial growth;

[0021] Epitaxially growing a GaN low-temperature buffer layer, an undoped GaN layer and an N-type doped GaN layer in sequence on the substrate, wherein the multi-quantum well layer is grown on the N-type doped GaN layer;

[0022] After the step of alternately growing quantum well layers and quantum barrier layers to prepare a multi-quantum well layer, the method further includes:

[0023] An electron blocking layer and a p-type doped GaN layer are sequentially epitaxially grown on the multi-quantum well layer.

[0024] A light emitting diode according to an embodiment of the present invention includes the above-mentioned GaN-based light emitting diode epitaxial wafer.

[0025] Compared with the prior art: the last quantum barrier is specially designed, specifically the last quantum barrier layer is divided into three sublayers; the first sublayer is an InN layer, the second sublayer is an InAlGaN layer, and the third sublayer is an AlN layer; when the second sublayer InAlGaN layer grows, the In component gradually decreases and the Al component gradually increases; the first sublayer is close to the quantum well layer and is grown using InN, which matches the InGaN quantum well layer very well, reducing the lattice mismatch between the two, avoiding the introduction of large strain and polarization electric field, reducing the potential barrier peak formed by the valence band of the electron blocking layer, and reducing the obstacle to hole injection; this layer is connected to the multi-quantum well layer, and the temperature is relatively low, which reduces the quantum well layer. The second sub-layer adopts an InAlGaN layer with gradual changes in In and Al components, in which the In component gradually decreases, so that the In component at the end close to the first sub-layer is higher, and the lattice is more matched with the first sub-layer InN layer, and the Al component gradually increases, so that the lattice is more matched with the third sub-layer AlN layer, reducing the generation of defects; the temperature of this layer is also gradually increased to improve the lattice quality; the third sub-layer is an AlN layer, and the high energy level of AlN can play the role of a partial electron blocking layer to prevent electrons from tunneling through the P layer, and the lattice mismatch between AlN and the subsequent sequentially grown electron blocking layer is small, reducing defects and increasing hole injection;

[0026] In general, the growth method of the last quantum barrier designed by the present invention improves the lattice matching between the quantum well layer and the P layer, and the energy level transition is gradual, which effectively reduces the barrier peak formed by the quantum well and the valence band of the electron blocking layer, which is beneficial to the injection of holes. At the same time, it plays the role of a partial electron blocking layer, reduces electron overflow, improves the luminous efficiency of the light-emitting diode, and is also beneficial to the improvement of its antistatic ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic structural diagram of a GaN-based light-emitting diode epitaxial wafer in the first embodiment of the present invention;

[0028] Figure 2It is a schematic diagram of the structure of the multi-quantum well layer in the first embodiment of the present invention.

[0029] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0030] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. Several embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0031] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0033] Embodiment 1

[0034] See also Figure 1 , shown is a GaN-based light-emitting diode epitaxial wafer in Example 1 of the present invention, including a substrate 1, and a GaN low-temperature buffer layer 2, an undoped GaN layer 3, an N-type doped GaN layer 4, a multi-quantum well layer 5, an electron blocking layer 6 and a p-type doped GaN layer 7 epitaxially grown on the substrate 1 in sequence.

[0035] Among them, Figure 2As shown, the multi-quantum well layer 5 is a periodic structure in which quantum well layers 51 and quantum barrier layers 52 are grown alternately. The quantum well layer 51 can be specifically an InGaN quantum well layer, and the other quantum barrier layers 52 except the last grown quantum barrier layer can be specifically a GaN quantum barrier layer or an InAlGaN quantum barrier layer. In the present embodiment, the last grown quantum barrier layer is specifically a composite quantum barrier layer 53, and the composite quantum barrier layer 53 specifically includes an InN sublayer 531, an InAlGaN sublayer 532, and an AlN sublayer 533 grown in sequence. In the present embodiment, the In component of the InAlGaN sublayer 532 gradually decreases along the epitaxial growth direction, and the Al component of the InAlGaN sublayer 532 gradually increases along the epitaxial growth direction. At the same time, the growth temperature of the AlN sublayer 533 is higher than the growth temperature of the InN sublayer 531, and the growth temperature of the InAlGaN sublayer 532 gradually increases.

[0036] It should be noted that the InN sublayer 531 is first grown on the last InGaN quantum well layer, and the InN and InGaN quantum well layers are well matched, which reduces the lattice mismatch between the two, avoids the introduction of large strain and polarization electric field, reduces the barrier peak formed by the 6th valence band of the electron blocking layer, and reduces the obstruction of hole injection; at the same time, this layer is connected to the quantum well layer 51, and the temperature is relatively low, which reduces the damage to the quantum well and avoids the decomposition of the In component of the InN sublayer. Then, after the InN sublayer 531, an InAlGaN layer with gradual changes in In and Al components is grown, wherein the In component gradually decreases, so that the In component at one end close to the InN sublayer 531 is higher, and the lattice is more matched with the InN sublayer 531, and the Al component gradually increases, so that the Al component at one end close to the subsequent AlN sublayer 533 is higher, and the lattice is more matched with the AlN sublayer 533, which reduces the generation of defects, and at the same time, the temperature of this layer is also gradually increased, which improves the lattice quality. Finally, an AlN layer is grown on the InAlGaN sublayer 532. The high energy level of AlN can play the role of a partial electron blocking layer 6 to block electrons from tunneling through the P layer. In addition, the lattice mismatch between AlN and the subsequently grown electron blocking layer 6 is small, which reduces defects and increases hole injection.

[0037] In some preferred cases of the present embodiment, the In component of the InAlGaN sublayer 532 gradually decreases from a first component value to 0 along the epitaxial growth direction, and the first component value is preferably 0.1-0.2, for example, 0.15 or 0.18; the Al component of the InAlGaN sublayer 532 gradually increases from 0 to a second component value along the epitaxial growth direction, and the second component value is preferably 0.1-0.3, for example, 0.2 or 0.25; the In component of the InN sublayer 531 is less than or equal to the first component value, for example, 0.1-0.2, and the Al component of the AlN sublayer 533 is 0.2-0.5. The growth temperature of the InAlGaN sublayer 532 gradually increases from the growth temperature of the InN sublayer 531 to the growth temperature of the AlN sublayer 533, that is, the InAlGaN sublayer 532 grows at the growth temperature of the InN sublayer 531 at the beginning, and then the growth temperature gradually increases, and finally the growth temperature reaches the growth temperature of the AlN sublayer 533. The growth temperature of the InN sublayer 531 is preferably 820-860°C, for example, 830°C or 850°C, and the growth temperature of the AlN sublayer 533 is 870-920°C, for example, 890°C or 910°C. Based on this component ratio and temperature control, a better energy level gradient transition effect is formed between the three sublayers, which greatly reduces the generation of lattice mismatch and lattice defects between each other, and greatly reduces the barrier peak formed by the quantum well and the valence band of the electron blocking layer 6.

[0038] In a specific implementation, the thickness of the composite quantum barrier layer 53 can be 8-15 nm, for example, 12 or 14 nm, wherein the thickness of the InN sublayer 531 is 0.5-3 nm, for example, 1 or 2 nm, the thickness of the InAlGaN sublayer 532 is 5-10 nm, for example, 6 or 8 nm, and the thickness of the AlN sublayer 533 is 0.5-3 nm, for example, 1 or 2 nm. Since the InAlGaN sublayer 532 plays a transition role between the AlN sublayer 533 and the InN sublayer 531, the thickness of the InAlGaN sublayer 532 is set to the maximum, which can give full play to the energy level transition effect of the InAlGaN sublayer 532. In addition, the alternating growth cycle of the multi-quantum well layer 515 can be 3 to 15, for example, 7 or 9, the thickness of the quantum well layer 51 in each cycle is about 2 to 4 nm, and the thickness of the quantum barrier layer 52 in each cycle except the last grown quantum barrier layer is 5 to 15 nm. In addition, the thickness of the GaN low-temperature buffer layer 2 can be 10 to 30 nm, for example, 15 or 25 nm, the thickness of the undoped GaN layer 3 can be about 1 to 5 μm, for example, 2 or 3 um, the N-type doped GaN layer 4 can specifically be a Si-doped GaN layer, and its thickness can be about 1 to 3 μm, for example, 2 or 2.5 um, the electron blocking layer 6 can be a superlattice structure of GaN and AlGaN, and the P-type doped GaN layer 7 has a thickness of about 50 to 300 nm, for example, 100 or 200 nm.

[0039] Embodiment 2

[0040] Embodiment 2 of the present invention provides a method for preparing a GaN-based light-emitting diode epitaxial wafer, which is used to prepare the GaN-based light-emitting diode epitaxial wafer in the above embodiment 1. The method specifically includes steps S21 to S28, wherein:

[0041] Step S21, providing a substrate required for epitaxial growth, preferably a sapphire substrate.

[0042] Specifically, the temperature of the reaction chamber is controlled to be 1050-1200° C., the substrate is subjected to high-temperature treatment for about 3-6 minutes in a hydrogen atmosphere, and the substrate is cleaned at high temperature to reduce impurities.

[0043] Step S22, growing a GaN low-temperature buffer layer on the sapphire substrate, with a growth temperature of 500° C. to 700° C. and a growth pressure of 200 to 400 Torr.

[0044] Exemplarily, the growth thickness of the GaN low-temperature buffer layer may be 10 to 30 nm.

[0045] Step S23, growing an undoped GaN layer on the GaN low-temperature buffer layer, with a growth temperature of 1000-1150° C. and a pressure of 200-400 Torr.

[0046] Exemplarily, the thickness of the undoped GaN layer is about 1-5 μm.

[0047] Step S24, growing an N-type doped GaN layer on the undoped GaN layer, with a growth temperature of 1000-1150° C. and a growth pressure of 200-400 Torr.

[0048] Exemplarily, the N-type doped GaN layer is a Si-doped GaN layer, and its thickness is about 1-3 μm.

[0049] Step S25, growing quantum well layers and quantum barrier layers alternately on the N-type doped GaN layer to prepare a multi-quantum well layer, and at the same time when growing the last quantum barrier layer: first, after the last quantum well layer is grown, the pressure remains unchanged, the temperature of the reaction chamber is controlled to 820-860° C., and an In source is introduced to grow an InN sublayer; secondly, a Ga source and an Al source are introduced, and the In source is continued to be introduced, and at the same time, the In source introduction amount is controlled to gradually decrease to 0, and the Al source introduction amount is gradually increased, and the temperature of the reaction chamber is controlled to gradually increase from the growth temperature of the InN sublayer to 870-920° C., so as to grow an InAlGaN sublayer with both Al and In components gradually changed; finally, the Ga source and the In source are turned off, and the Al source is kept introduced to grow the AlN sublayer at a reaction chamber temperature of 870-920° C.

[0050] For example, the number of quantum well layers in the multi-quantum well layer can be 3 to 15 layers, and the growth pressure of the multi-quantum well layer is 100 to 500 Torr. The thickness of the quantum well layer in each period is about 2 to 4 nm, and the growth temperature can be 700 to 800° C.; the thickness of the quantum barrier layer in each period except the last quantum barrier layer is 5 to 15 nm, and the growth temperature is 850 to 950° C. The growth temperature of the last quantum barrier layer can be 800 to 950° C.

[0051] Step S26, growing an electron blocking layer on the multi-quantum well layer, with a growth temperature of 800-1000° C. and a growth pressure of 100-300 Torr.

[0052] Exemplarily, the electron blocking layer may be a superlattice structure of GaN and AlGaN.

[0053] Step S27, growing a P-type doped GaN layer on the electron blocking layer, wherein the growth temperature is about 800-1000° C. and the growth pressure is 100-300 torr.

[0054] Exemplarily, the P-type doped GaN layer has a thickness of about 50 to 300 nm.

[0055] In summary, the GaN-based light-emitting diode epitaxial wafer in the embodiment of the present invention is specially designed for the last quantum barrier, specifically, the last quantum barrier layer is divided into three sublayers; the first sublayer is an InN layer, the second sublayer is an InAlGaN layer, and the third sublayer is an AlN layer; when the second sublayer InAlGaN layer grows, the In component gradually decreases and the Al component gradually increases; the first sublayer is close to the quantum well layer, and is grown using InN, which is well matched with the InGaN quantum well layer, reducing the lattice mismatch between the two, avoiding the introduction of large strain and polarization electric field, reducing the potential barrier peak formed by the valence band of the electron blocking layer, and reducing the obstacle to hole injection; this layer is connected to the multi-quantum well layer, and the temperature is relatively stable. The temperature of the first sublayer is lower, which reduces the damage to the quantum well and avoids the decomposition of the In component of the InN layer. The second sublayer adopts an InAlGaN layer with a gradient of In and Al components, in which the In component gradually decreases, so that the In component at the end close to the first sublayer is higher, and the lattice is more matched with the first sublayer InN layer. The Al component gradually increases, and the lattice is more matched with the third sublayer AlN layer, which reduces the generation of defects. The temperature of this layer also increases gradually to improve the lattice quality. The third sublayer is an AlN layer, and the high energy level of AlN can play the role of a partial electron blocking layer to prevent electrons from tunneling through the P layer. The lattice mismatch between AlN and the subsequent sequentially grown electron blocking layer is small, which reduces defects and increases hole injection.

[0056] In general, the growth method of the last quantum barrier designed by the present invention improves the lattice matching between the quantum well layer and the P layer, and the energy level transition is gradual, which effectively reduces the barrier peak formed by the quantum well and the valence band of the electron blocking layer, which is beneficial to the injection of holes. At the same time, it plays the role of a partial electron blocking layer, reduces electron overflow, improves the luminous efficiency of the light-emitting diode, and is also beneficial to the improvement of its antistatic ability.

[0057] Embodiment 3

[0058] The third embodiment of the present invention provides a light emitting diode, including the GaN-based light emitting diode epitaxial wafer in the above embodiment 1, and the GaN-based light emitting diode epitaxial wafer can be obtained by epitaxial growth using the preparation method of the GaN-based light emitting diode epitaxial wafer in the above embodiment 2.

[0059] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A GaN-based light-emitting diode epitaxial wafer, characterized in that: It includes a multi-quantum well layer, wherein the multi-quantum well layer is a periodic structure in which quantum well layers and quantum barrier layers are grown alternately; Among them, the last quantum barrier layer grown is a composite quantum barrier layer, which includes an InN sublayer, an InAlGaN sublayer and an AlN sublayer grown in sequence, the In component of the InAlGaN sublayer gradually decreases along the epitaxial growth direction, and the Al component of the InAlGaN sublayer gradually increases along the epitaxial growth direction.

2. The GaN-based light-emitting diode epitaxial wafer according to claim 1, characterized in that: The growth temperature of the AlN sublayer is higher than the growth temperature of the InN sublayer, and the growth temperature of the InAlGaN sublayer increases gradually.

3. The GaN-based light-emitting diode epitaxial wafer according to claim 2, characterized in that: The growth temperature of the InAlGaN sublayer gradually increases from the growth temperature of the InN sublayer to the growth temperature of the AlN sublayer, the growth temperature of the InN sublayer is 820-860°C, and the growth temperature of the AlN sublayer is 870-920°C.

4. The GaN-based light-emitting diode epitaxial wafer according to claim 1, characterized in that: The In component of the InAlGaN sublayer gradually decreases from a first component value to 0 along the epitaxial growth direction; The Al component of the InAlGaN sublayer gradually increases from 0 to a second component value along the epitaxial growth direction; Among them, the first component value is 0.1-0.2, and the second component value is 0.1-0.

3.

5. The GaN-based light-emitting diode epitaxial wafer according to claim 4, characterized in that: The In component of the InN sublayer is less than or equal to the first component value, and the Al component of the AlN sublayer is 0.2-0.

5.

6. The GaN-based light-emitting diode epitaxial wafer according to claim 1, characterized in that: The thickness of the composite quantum barrier layer is 8-15 nm, wherein the thickness of the InN sublayer is 0.5-3 nm, the thickness of the InAlGaN sublayer is 5-10 nm, and the thickness of the AlN sublayer is 0.5-3 nm.

7. The GaN-based light-emitting diode epitaxial wafer according to any one of claims 1 to 6, characterized in that: It also includes a substrate, a GaN low-temperature buffer layer, an undoped GaN layer, an N-type doped GaN layer, an electron blocking layer and a p-type doped GaN layer; The GaN low-temperature buffer layer, the undoped GaN layer, the N-type doped GaN layer, the multi-quantum well layer, the electron blocking layer and the p-type doped GaN layer are epitaxially grown in sequence on the substrate.

8. A method for preparing a GaN-based light-emitting diode epitaxial wafer, characterized in that: Used to prepare the GaN-based light-emitting diode epitaxial wafer according to any one of claims 1 to 7, the preparation method comprising: Alternately grow quantum well layers and quantum barrier layers to prepare multiple quantum well layers. When growing the last quantum barrier layer: First, the In source is introduced to grow the InN sublayer, and then the Ga source and Al source are introduced, and the In source is continued to be introduced, while the In source input is controlled to gradually decrease and the Al source input is gradually increased to grow an InAlGaN sublayer with gradual changes in Al and In components. Finally, the Ga source and In source are turned off, and the Al source is kept introduced to grow the AlN sublayer.

9. The method for preparing a GaN-based light-emitting diode epitaxial wafer according to claim 8, characterized in that: Before the step of alternately growing quantum well layers and quantum barrier layers to prepare a multi-quantum well layer, the method further includes: Providing a substrate for epitaxial growth; Epitaxially growing a GaN low-temperature buffer layer, an undoped GaN layer and an N-type doped GaN layer in sequence on the substrate, wherein the multi-quantum well layer is grown on the N-type doped GaN layer; After the step of alternately growing quantum well layers and quantum barrier layers to prepare a multi-quantum well layer, the method further includes: An electron blocking layer and a p-type doped GaN layer are sequentially epitaxially grown on the multi-quantum well layer.

10. A light emitting diode, characterized in that: The invention comprises the GaN-based light-emitting diode epitaxial wafer as described in any one of claims 1 to 7.

Images