Epitaxial layer structure, growth method and chip of a nitride optoelectronic device

Abstract

The present application provides an epitaxial layer structure, a growth method and a chip of a nitride optoelectronic device. The epitaxial layer structure includes: a substrate, a P-type region layer, a quantum modulation layer, a light-emitting active region and an N-type region layer stacked in sequence. The epitaxial layer structure adopts a P-type inverted nitride optoelectronic device, which can obtain a high-quality P-type region, and can be grown at a high temperature to obtain high crystal quality and doping effect. At the same time, the epitaxial layer structure is simplified.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductors, and particularly relates to an epitaxial layer structure, a growth method, and a chip of a P-type inverted nitride optoelectronic device. Background Art

[0002] Nitrides represented by gallium nitride are wide-bandgap, direct-bandgap semiconductor materials, which are the material system with the widest bandgap crossing, and are very suitable for fabricating optoelectronic devices covering the ultraviolet to infrared bands. With the breakthrough of key material problems such as P-type gallium nitride activation at the end of the last century, the LED applications for general lighting have been widely developed. The current structure of GaN-based optoelectronic devices is "substrate - N-type region - light-emitting active region - P-type region", following the traditional PN junction structure. As Figure 1 shown, the current epitaxial full structure is "substrate - N-type region - stress relaxation layer (SRL) - light-emitting active region (MQWs) - electron blocking layer (EBL) - P-type region". Taking GaN-based LEDs on sapphire substrates as an example, the energy band analysis is as Figure 2 shown. After growing the N-type GaN region at high temperature on the sapphire substrate, the light-emitting active region is generally an InGaN / GaN multiple quantum well structure (MQWs). In order to improve its quality, a stress relaxation layer (SRL) is grown at medium temperature after the N-type region. The stress relaxation layer is generally a relatively thick InGaN material, and the In composition of the InGaN material here is lower than that of the light-emitting active region. The purpose is to perform stress regulation on the epitaxial layer, making the quantum wells of the truly grown light-emitting active region have less stress and a flatter interface. At the same time, the stress relaxation layer also has the function of opening V-shaped pits to increase the area of the light-emitting active region and improve the light-emitting efficiency. After the low-temperature light-emitting active region, in order to protect the quantum wells, an electron blocking layer (EBL) is grown at medium temperature, generally an AlGaN material with a higher potential barrier, which functions to block the electrons overflowing from the N-type region to the active region and reduce leakage, etc. Then, the P-type GaN region is still grown at medium temperature. However, the light-emitting active region is generally composed of materials such as InGaN, and the growth temperature of the active region is relatively low, and high temperature will also damage the active region, causing phenomena such as In precipitation. Therefore, the growth temperature of the P-type region in the current structure cannot be high, and it can only be grown at a reduced temperature (generally at 950 °C); while the N-type region can be grown at the normal growth temperature of GaN materials (generally 1050 - 1100 °C) because it is grown before the light-emitting active region. The result is that the growth quality of the N-type region is good, while the quality of the P-type region is poor. Moreover, the activation energy of the doped Si element in the N-type is very low, and the activation energy of the doped Mg element in the P-type is relatively high, corresponding to a low activation concentration in the P-type and a high activation concentration in the N-type. This causes an obvious "N strong P weak" phenomenon in nitride optoelectronic devices, restricting the development of devices towards higher performance. Summary of the Invention

[0003] To overcome the above-mentioned drawbacks, the purpose of this application is to provide a P-type inverted nitride optoelectronic device, which can be grown at high temperature to obtain high crystal quality and doping effect. At the same time, it overcomes the disadvantage that it is difficult to improve the optoelectronic efficiency in the existing P-type region.

[0004] To achieve the above purpose, the technical solution adopted in this application is as follows:

[0005] An epitaxial layer structure of a nitride optoelectronic device, characterized by comprising:

[0006] A substrate, a P-type region layer, a quantum modulation layer, a light-emitting active region, and an N-type region layer,

[0007] Among them, the P-type region layer is stacked on the substrate, the quantum modulation layer is stacked on the P-type region layer, the light-emitting active region is stacked on the quantum modulation layer, and the N-type region layer is stacked on the light-emitting active region. This epitaxial layer structure adopts a P-type inverted nitride optoelectronic device, which can obtain a high-quality P-type region, can be grown at high temperature to obtain high crystal quality and doping effect, and simplifies the epitaxial layer structure at the same time.

[0008] Preferably, the quantum modulation layer includes a cyclic structure of AlGaN / InGaN combination.

[0009] Preferably, the cyclic structure is formed by periodically stacking AlGaN / InGaN, and the cyclic structure is used as the superlattice or quantum well structure of the quantum modulation layer.

[0010] Preferably, the cyclic structure is formed by stacking 10 to 50 (such as 30) alternating periods of AlGaN / InGaN.

[0011] Preferably, the substrate is a sapphire substrate, a silicon substrate, or a silicon carbide substrate.

[0012] Preferably, the N-type region layer is bonded to a heat dissipation substrate.

[0013] The embodiment of this application provides a growth method for an epitaxial layer structure of a nitride optoelectronic device, characterized in that the method includes the following steps:

[0014] S1. Grow a P-type region layer on the substrate,

[0015] S2. Grow a quantum modulation layer on the P-type region layer,

[0016] S3. Grow a light-emitting active region on the quantum modulation layer,

[0017] S4. Grow an N-type region layer on the light-emitting active region.

[0018] The substrate is preferably a sapphire substrate.

[0019] Preferably, in step S1, Mg-doped p-type GaN is grown at a temperature of 1050°C - 1100°C.

[0020] Preferably, the growth of the quantum modulation layer in step S2 includes a cyclic structure of AlGaN / InGaN grown by combining high and low temperatures.

[0021] Preferably, the high and low temperature combination growth includes:

[0022] After growing a certain thickness of the AlGaN layer in the first temperature range of 850°C - 1000°C,

[0023] The temperature is then lowered to the second temperature range of 700°C - 850°C to grow a certain thickness of the InGaN material layer.

[0024] An embodiment of the present application provides a chip, characterized in that it has an epitaxial layer structure made by the above method.

[0025] Preferably, the n-type region layer is directly bonded to the heat dissipation substrate.

[0026] Beneficial effects

[0027] Compared with the prior art, the epitaxial layer structure of the p-type inverted nitride optoelectronic device in the embodiment of the present application first grows the p-type region on the substrate to obtain a high-quality p-type region, and obtains high crystal quality and doping effect through high-temperature growth. It overcomes the drawbacks of low carrier concentration and difficulty in improving optoelectronic efficiency caused by low crystal quality of the existing p-type region. This epitaxial structure is particularly suitable for vertical structure chip applications, such as Micro-LEDs, etc. At this time, the n-type region can be directly bonded to the heat dissipation substrate. Description of the drawings

[0028] Figure 1 Schematic diagram of the existing full epitaxial layer structure;

[0029] Figure 2 Schematic diagram of the energy band analysis of the epitaxial layer structure of the existing sapphire substrate structure;

[0030] Figure 3 Schematic diagram of the full epitaxial layer structure of the embodiment of the present application;

[0031] Figure 4 Schematic diagram of the energy band analysis of the full epitaxial layer structure of the embodiment of the present application;

[0032] Figure 5 Schematic diagram of the superposition of the EL spectra of the full epitaxial layer structure of the embodiment of the present application and the existing full epitaxial layer structure;

[0033] Figure 6Schematic flow of the growth method for the entire epitaxial layer structure of the embodiments of the present application. Detailed implementation manners

[0034] The above solution will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are for illustrating the present application and not for limiting the scope of the present application. The implementation conditions adopted in the embodiments can be further adjusted according to the conditions of specific manufacturers, and the implementation conditions not specified are usually those in conventional experiments.

[0035] The present application provides an epitaxial layer structure of a nitride optoelectronic device, which includes: a substrate, a P-type region layer, a quantum modulation layer, a light-emitting active region, and an N-type region layer stacked in sequence. This epitaxial layer structure adopts a P-type inverted nitride optoelectronic device, which can obtain a high-quality P-type region, can be grown at a high temperature to obtain high crystal quality and doping effect, and simplifies the epitaxial layer structure.

[0036] As Figure 3 shown is a schematic diagram of the epitaxial structure of the nitride optoelectronic device proposed by the present application.

[0037] The nitride optoelectronic device includes:

[0038] a substrate 1, a P-type region layer 2, a quantum modulation layer 3, a light-emitting active region 4, and an N-type region layer 5.

[0039] Among them, the P-type region layer 2 is stacked on the substrate 1, the quantum modulation layer 3 is stacked on the P-type region layer 2, the light-emitting active region 4 is stacked on the quantum modulation layer 3, and the N-type region layer 5 is stacked on the light-emitting active region 4. Compared with the current entire epitaxial structure of "substrate - N-type region - stress relief layer (SRL) - light-emitting active region (MQWs) - electron blocking layer (EBL) - P-type region", this nitride optoelectronic device can obtain a high-quality P-type region layer, overcoming the drawback that it is difficult to improve the optoelectronic efficiency when the P-type layer is below. The nitride optoelectronic device of the implementation manner of the present application can grow a P-type region with high crystal quality and high activation efficiency in a high-temperature environment. For the energy band analysis, see Figure 4 .

[0040] The quantum modulation layer (QML) is a cyclic structure of AlGaN / InGaN grown at high and low temperatures. The cyclic structure is AlGaN / InGaN / AlGaN / InGaN... stacked periodically (preferably, between 10 and 50 alternating periods, such as 30 periods), and this cyclic structure is used as the superlattice or quantum well structure of the quantum modulation layer. Its function is to achieve the growth of high and low potential barrier wells with a large energy band difference. The high potential barrier is used to block the overflow electrons, and the low potential well is used for stress relaxation, integrating the functions of the stress release layer and the electron blocking layer. The height of the potential barrier and potential well and the stress regulation in the epitaxial layer can be adjusted by adjusting the thickness and Al composition of AlGaN and the thickness and In composition of InGaN in AlGaN / InGaN, etc., so as to block the electron flow under different chip working conditions and release the stress in advance for different quantum well structures, with very high operability. The dual technical problems of blocking the electron overflow after P-type inversion and stress release before growing the high In composition active region are solved by this quantum modulation layer.

[0041] After that, a high-quality InGaN / GaN active region structure is grown at low temperature,

[0042] Then, an N-type GaN region is grown at medium temperature. Since there is no need to grow an electron blocking layer, the damage to the active region structure is less, which is suitable for growing LEDs with high In composition and long wavelength segments.

[0043] In one embodiment, when the device is used in the vertical structure chip scenario, the N-type region can be directly bonded to the heat dissipation substrate.

[0044] This application proposes a growth method for the epitaxial structure of the above nitride optoelectronic device. The method includes the following steps (see Figure 6 ):

[0045] S1. Grow a P-type region layer on the substrate,

[0046] S2. Grow a quantum modulation layer on the P-type region layer,

[0047] S3. Grow a light-emitting active region on the quantum modulation layer,

[0048] S4. Grow an N-type region layer on the light-emitting active region.

[0049] The substrate is preferably a sapphire substrate. In other embodiments, the substrate is a silicon substrate or a silicon carbide substrate.

[0050] Step S1 includes growing Mg-doped P-type GaN at 1080 °C.

[0051] In step S2, the growth of the quantum modulation layer includes a cyclic structure of AlGaN / InGaN grown by combining high and low temperatures. Specifically, it includes growing a certain thickness of the AlGaN layer in the first temperature range of 850°C - 1000°C and then cooling down to the second temperature range of 700°C - 850°C to grow a certain thickness of the InGaN material layer, and repeating this growth cycle. When the stress release is relatively large and the growth temperature of InGaN is relatively low, the cycle can be split into three-stage growth in the form of AlGaN / InGaN / AlGaN, where the growth temperature of the second AlGaN is between that of the first AlGaN and InGaN. The purpose is to protect the high-In-component InGaN and improve its crystal quality. Through the cyclic structure of AlGaN / InGaN grown by combining high and low temperatures, the growth of high and low potential barrier wells with large energy band differences is achieved. The high potential barrier is used to block the overflow electrons, and the low potential well is used for stress relaxation, integrating the functions of the stress release layer and the electron blocking layer. This solves the two technical problems of P-type growth on the substrate, the need to block electron overflow, and the need for stress release before growing the high-In-component active region.

[0052] After the growth of the quantum modulation layer, a light-emitting active region with a preset number of cycles (such as 5 cycles) of InGaN / GaN quantum well structure is grown. Then, the temperature is lowered to grow a certain thickness of Si-doped N-type GaN layer.

[0053] The following combines specific embodiments to verify the effects of the nitride optoelectronic device proposed in this application.

[0054] The experiment was based on a sapphire substrate, and a comparative experiment on the epitaxial growth of two blue-band LEDs with a conventional epitaxial structure and the epitaxial structure of this application was carried out.

[0055] The solution of the prior art is: an epitaxial structure of "substrate - N-type region - stress release layer (SRL) - light-emitting active region (MQWs) - electron blocking layer (EBL) - P-type region". According to the prior art solution, after growing a buffer layer and three-dimensional growth on the sapphire substrate until the growth of a two-dimensional GaN bulk material, a Si-doped N-type GaN layer of about 2 μm is grown at 1060°C. Then, 150 nm of InGaN material is grown at 900°C. Then, the temperature is lowered to 750°C and 830°C to grow 3 nm of InGaN and 12 nm of GaN as the quantum well and quantum barrier respectively, and the growth is repeated for 5 cycles. Then, the temperature is raised to 960°C to grow a 100 nm Mg-doped P-type AlGaN layer and a 100 nm P-type GaN layer. For the convenience of description, the epitaxial structure generated by this prior art process is denoted as sample A.

[0056] This solution adopts an epitaxial structure of "substrate - P - type region - quantum modulation layer (QML) - light - emitting active region (MQWs) - N - type region". The growth conditions of the bulk GaN material are consistent. At 1060 °C, about 2 μm of Mg - doped P - type GaN is grown, and then at 950 °C, 760 °C, and 830 °C respectively, 1.5 nm of AlGaN, 2 nm of InGaN, and 1.5 nm of AlGaN materials are grown, with a total of 30 cycles. Then, a 5 - cycle InGaN / GaN quantum well structure is grown under the same conditions as sample A, and then the temperature is reduced to 960 °C to grow a 200 - nm Si - doped N - type GaN layer. For the convenience of description, the epitaxial structure generated by this solution is denoted as sample B.

[0057] Electroluminescence tests are respectively carried out on sample A and sample B. The driving current for the test is 200 mA, and the spectra are as Figure 5 shown, Figure 5 in which the superposition of the EL spectra of the two is shown. It can be clearly seen that the intensity of sample B has increased. Therefore, the nitride optoelectronic device with a P - type inverted structure proposed in this application has certain advantages in terms of optical efficiency compared with the current structure.

[0058] The above - mentioned embodiments are only for illustrating the technical concept and characteristics of this application. The purpose is to enable those who are familiar with this technology to understand the content of this application and implement it accordingly, and it cannot be used to limit the protection scope of this application. Any equivalent transformation or modification made in the spirit of this application should be covered within the protection scope of this application.

Claims

1. An epitaxial layer structure of a nitride optoelectronic device, characterized in that, Including: a substrate, a P-type region layer, a quantum modulation layer, a light-emitting active region, and an N-type region layer wherein, the P-type region layer is stacked on the substrate, the quantum modulation layer is stacked on the P-type region layer, the light-emitting active region is stacked on the quantum modulation layer, and the N-type region layer is stacked on the light-emitting active region; and the light-emitting active region is in direct contact with the N-type region layer; wherein, the growth temperature of the P-type region layer is 1050°C - 1100°C, and the P-type region layer is Mg-doped P-type GaN; the quantum modulation layer is a cyclic structure of AlGaN / InGaN grown by a combination of high and low temperatures, and the cyclic structure is used to realize the growth of high and low potential barrier wells, the high potential barrier is used to block overflow electrons, and the low potential well is used for stress relaxation; wherein, the combination of high and low temperature growth is: after growing a first AlGaN layer with a certain thickness in the first temperature range of 850°C - 1000°C, then cooling to the second temperature range of 700°C - 850°C to grow a certain thickness of InGaN material layer, and then heating up to grow a second AlGaN layer, and so on in a cycle; the growth temperature of the second AlGaN layer is greater than the growth temperature of the InGaN material layer, and the growth temperature of the second AlGaN layer is less than the growth temperature of the first AlGaN layer.

2. The epitaxial layer structure of the nitride optoelectronic device according to claim 1, characterized in that, The substrate is a sapphire substrate, a silicon substrate, or a silicon carbide substrate.

3. The epitaxial layer structure of the nitride optoelectronic device according to claim 1, characterized in that, The N-type region layer is bonded to a heat dissipation substrate.

4. A method for growing an epitaxial layer structure of a nitride optoelectronic device, characterized in that, The method includes the following steps: S1. Under high temperature conditions of 1050°C - 1100°C, grow Mg-doped P-type GaN on the substrate to obtain a P-type region layer, S2. Grow a quantum modulation layer on the P-type region layer, S3. Grow a light-emitting active region on the quantum modulation layer, S4. Grow an N-type region layer on the light-emitting active region, and the light-emitting active region is in direct contact with the N-type region layer; wherein, the quantum modulation layer is a cyclic structure of AlGaN / InGaN grown by a combination of high and low temperatures, and the cyclic structure is used to realize the growth of high and low potential barrier wells, the high potential barrier is used to block overflow electrons, and the low potential well is used for stress relaxation; wherein, the combination of high and low temperature growth is: after growing a first AlGaN layer with a certain thickness in the first temperature range of 850°C - 1000°C, then cooling to the second temperature range of 700°C - 850°C to grow a certain thickness of InGaN material layer, and then heating up to grow a second AlGaN layer, and so on in a cycle; wherein, the growth temperature of the second AlGaN layer is greater than the growth temperature of the InGaN material layer, and the growth temperature of the second AlGaN layer is less than the growth temperature of the first AlGaN layer.

5. A chip, characterized in that, Having an epitaxial layer structure made by the method of claim 4.

6. The chip according to claim 5, wherein The N-type region layer is directly bonded to a heat dissipation substrate.

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