High-power non-polar ultraviolet LED based on transversely-growing AlGaN / GaN heterojunction and preparation method of high-power non-polar ultraviolet LED
By establishing multiple conductive channels in AlGaN/GaN heterojunction and using non-polar quantum wells, combined with diamond substrates, the internal quantum efficiency and heating problems of AlGaN-based UV LED are solved, and efficient carriers are achieved Injection and performance improvements.
Patent Information
- Application Number
- CN202411201925.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-29
- Publication Date
- 2024-12-06
AI Technical Summary
AlGaN-based ultraviolet LEDs have serious problems with low internal quantum efficiency, low hole concentration and low conductivity of p-type AlGaN, and current congestion effects, which limit their efficient development.
Using high-power non-polar ultraviolet LED based on lateral growth of AlGaN/GaN heterojunction, multiple conductive channels are established in the n-type region and the p-type region, and the carrier injection efficiency is improved by using the polarization effect, and in the quantum The well region uses non-polar AlGaN to eliminate the quantum restricted Stark effect, and combines the diamond substrate to enhance heat dissipation.
It improves the internal quantum efficiency and carrier injection efficiency of ultraviolet LEDs, reduces heating, and improves the overall performance of the device.
Smart Images
Figure CN119092607A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of semiconductor technology, and in particular relates to a high-power non-polar ultraviolet LED based on a lateral growth AlGaN / GaN heterojunction and a method. Background Art
[0002] Since the research on two-dimensional electron gas in GaN-based semiconductors made progress in the 1990s, high electron mobility transistors represented by AlGaN / GaN heterostructures have shined in high-power and high-frequency applications in recent years. MS Shur and M. Shatalov proposed the use of p-GaN / p-AlGaN single heterojunctions to achieve a large number of holes at the heterojunction interface. At the same time, due to the existence of a single barrier and the effects of tunneling and thermal emission, the vertical conductivity is improved. However, the defect is that the hole ionization rate is still low, resulting in poor ohmic contact of p-type GaN.
[0003] In the current mainstream preparation method, there is a quantum confined Stark effect caused by a strong polarization effect in the quantum well region of the UV LED, which in turn makes the quantum efficiency of the UV LED low. In recent years, researchers have paid more and more attention to non-polar and semi-polar GaN-based LED devices. Since the growth direction of the quantum well is perpendicular to the polarization direction, there is no polarization electric field in the active region or the influence of the polarization electric field can be ignored. At present, there have been a lot of studies on non-polar InGaN-based green light LEDs, but there are few reports on non-polar AlGaN quantum wells.
[0004] The AlGaN material used in ultraviolet LEDs has a strong spontaneous polarization effect, which can easily generate a strong polarization electric field in the quantum well region, resulting in band bending and separation of electron and hole wave functions, namely the quantum confined Stark effect, which makes AlGaN-based ultraviolet LEDs face the problem of low internal quantum efficiency.
[0005] At the same time, since Mg in p-type AlGaN is in a deep acceptor level, the ionization rate of Mg in p-type doped AlGaN material is low, resulting in low hole concentration and low conductivity of p-type AlGaN. Therefore, the low hole injection rate of AlGaN-based UV LEDs is another problem that restricts the development of high-efficiency UV LEDs.
[0006] For AlGaN-based optoelectronic devices, the low and asymmetric electron and hole concentrations will cause the electrons injected into the active region to leak into the p-type region. The current expansion difference between the n-type and p-type regions will produce current congestion effect and heat accumulation, which will ultimately lead to severe heating of the device and low luminous efficiency. Summary of the invention
[0007] In order to overcome the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a high-power non-polar ultraviolet LED and method based on a laterally grown AlGaN / GaN heterojunction, wherein multiple conductive channels are established by laterally growing a periodic AlGaN / GaN heterojunction, and the carrier injection efficiency in the quantum well is improved by utilizing the polarization effect. At the same time, non-polar AlGaN is used in the quantum well region to overcome the influence of the quantum confined Stark effect, and finally a diamond substrate is used to enhance the heat dissipation.
[0008] In order to achieve the above object, the technical solution adopted by the present invention is:
[0009] The high-power non-polar ultraviolet LED based on the laterally grown AlGaN / GaN heterojunction includes a substrate layer, a buffer layer, an n-type region, a multi-quantum well layer and a p-type region from bottom to top, and is characterized by:
[0010] The n-type region is a laterally grown periodic n-type AlGaN / GaN heterojunction, and the p-type region is a laterally grown periodic p-type AlGaN / GaN heterojunction.
[0011] The substrate layer is diamond, which further enhances the thermal conductivity of the device.
[0012] The buffer layer is non-polar GaN, which generally has poor quality. The buffer layer is first grown at a suitable temperature so that the nucleation islands of the buffer layer are large and sparsely distributed, and then the high-temperature growth tends to grow more laterally, which is used to provide nucleation sites for the epitaxial growth of non-polar GaN and improve the crystal quality of the non-polar GaN epitaxial layer.
[0013] The laterally grown periodic n-type AlGaN / GaN heterojunction is formed by etching, regrowth and n-type doping, with a doping concentration of 10 16 -10 18 cm -3 Due to spontaneous polarization and piezoelectric polarization, the laterally alternatingly grown AlGaN / GaN heterojunction produces a high surface density of net bound positive charges at the heterojunction interface, which attracts negatively charged charges and forms multiple two-dimensional electron gas conductive channels, which is equivalent to increasing the carrier concentration of the donor.
[0014] The multi-quantum well layer is non-polar Al x Ga 1-x N / A y Ga 1-y N, confines the non-equilibrium carriers in the well layer, where electrons and holes undergo radiative recombination and emit photons. At the same time, the non-polar quantum well eliminates the influence of the quantum confinement Stark effect, greatly improving the luminescence efficiency, so it is the main structure for the device to emit light.
[0015] The laterally grown periodic p-type AlGaN / GaN layer is formed by etching, regrowth and p-type doping, and the doping concentration is 10 17 -10 19 cm -3 Due to spontaneous polarization and piezoelectric polarization, the laterally alternating AlGaN / GaN heterojunction produces a high surface density of net bound negative charges at the heterojunction interface, which attracts positive charges and forms multiple two-dimensional hole gas conduction channels, which is equivalent to increasing the carrier concentration of the acceptor.
[0016] The thickness of the non-polar GaN buffer layer is 3-4 μm.
[0017] The laterally grown periodically alternating n-type AlGaN / GaN heterojunction layer has a thickness of 1-2 μm and a period number of 5-10.
[0018] The non-polar Al x Ga 1-x N / A y Ga 1-y N multi-quantum well layer, the thickness of which is 100-300nm; each period of Al x Ga 1-x N well layer and Al y Ga 1-y The thickness of the N barrier layer is 5-10nm and 15-20nm respectively, the adjustment range of Al content x is 0.0-0.5, and the adjustment range of Al content y is 0.1-0.6. The purpose is to set the quantum well emission wavelength to the ultraviolet light band.
[0019] The p-type AlGaN / GaN heterojunction layer that is grown laterally and grown periodically and alternately has a thickness of 1-2 μm and a period number of 5-10.
[0020] A method for preparing a high-power non-polar ultraviolet LED based on a laterally grown AlGaN / GaN heterojunction comprises the following steps:
[0021] 1) Cleaning and drying the substrate;
[0022] 2) Using MOCVD to grow a GaN buffer layer with a thickness of 4-5 μm;
[0023] 3) A GaN groove with a thickness of 1-2 μm is etched on the GaN buffer layer by an etching process;
[0024] 4) Then, an MOCVD process is used to grow AlGaN with the same thickness as the groove on the etched GaN sidewall, forming an AlGaN / GaN heterojunction with a periodic lateral growth of 1-2 μm;
[0025] 5) Using MOCVD to grow 5-10 cycles of non-polar Al on the laterally grown AlGaN / GaN heterojunction n-type layer x Ga 1-x N / A y Ga 1-y N multi-quantum well layer, Al x Ga 1-x The thickness of the N quantum well is 5-10nm, and the Al y Ga 1-y The thickness of the N quantum barrier is 15-20 nm, the adjustment range of the Al content x is 0.05-0.5, and the adjustment range of the Al content y is 0.15-0.6;
[0026] 6) growing a 1-2 μm GaN layer on the last quantum barrier layer and etching a GaN groove using an etching process until the last quantum barrier layer is exposed;
[0027] 7) Grow a laterally grown periodic p-type AlGaN / GaN layer. Use the MOCVD process to grow AlGaN with the same thickness as the groove on the etched GaN sidewall, forming a periodically laterally grown AlGaN / GaN heterojunction as the p-type region of the device, and obtaining a high-power non-polar ultraviolet LED.
[0028] Epitaxial growth can also be accomplished using MBE.
[0029] The high-power non-polar ultraviolet LED structure based on the laterally grown AlGaN / GaN heterojunction first uses a diamond substrate to enhance heat dissipation, then uses laterally grown periodically alternating p-type and n-type AlGaN / GaN heterojunction layers to enhance carrier injection efficiency, and finally uses a non-polar quantum well structure to improve luminous efficiency.
[0030] Beneficial effects of the present invention:
[0031] 1. Compared with conventional sapphire substrates, diamond substrates are innovatively used. Diamond substrates have good thermal conductivity and are suitable for use in high-power LEDs.
[0032] 2. The present invention innovatively uses laterally grown periodic n-type AlGaN / GaN layers and p-type AlGaN / GaN layers to establish multiple two-dimensional electron gas and two-dimensional hole gas conductive channels respectively, and at the same time uses the polarization effect to improve the ionization rate of electrons and holes, thereby improving the problem of low carrier injection efficiency of traditional AlGaN-based ultraviolet LEDs.
[0033] 3. The present invention uses non-polar Al x Ga 1-x N / A y Ga 1-yThe N multi-quantum well layer eliminates the influence of the quantum confinement Stark effect in traditional ultraviolet LEDs and helps to improve the internal quantum efficiency of the device.
[0034] The present invention utilizes both polarization effect and non-polarization effect, and establishes multiple two-dimensional electron gas and two-dimensional hole gas conductive channels in the n-type region and the p-type region respectively by using the laterally grown periodic AlGaN / GaN heterostructure, and simultaneously utilizes the polarization effect to improve the ionization rate and enhance the n-type and p-type doping efficiency, while non-polar AlGaN is used in the quantum well region to eliminate the quantum confinement Stark effect, thereby improving the internal quantum efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0035] Figure 1 It is a schematic diagram of the structure of a high-power non-polar ultraviolet LED of the present invention.
[0036] Figure 2 It is a process flow chart of the present invention for making a high-power non-polar ultraviolet LED structure. DETAILED DESCRIPTION
[0037] The present invention will be further described in detail below in conjunction with the accompanying drawings.
[0038] like Figure 1 As shown in the figure, a high-power non-polar ultraviolet LED based on a laterally grown AlGaN / GaN heterojunction includes, from bottom to top, a diamond substrate, a non-polar GaN buffer layer, a laterally grown periodic n-type AlGaN / GaN layer, a non-polar Al x Ga 1-x N / A y Ga 1-y N multiple quantum well layer and a laterally grown periodic p-type AlGaN / GaN layer.
[0039] The n-type AlGaN / GaN heterostructure has spontaneous polarization and piezoelectric polarization, and the GaN in the n-type layer is thicker and in a relaxed state, generating multiple two-dimensional electron gas conduction channels at the interface of the AlGaN / GaN heterostructure.
[0040] There is spontaneous polarization and piezoelectric polarization in the p-type GaN / AlGaN heterostructure, and the AlGaN in the p-type layer is thicker and in a relaxed state, so multiple two-dimensional hole gas conduction channels are generated at the interface of the AlGaN / GaN heterostructure.
[0041] When voltage is applied to both ends of the light-emitting diode, carriers are injected into the non-polar quantum well through multiple conductive channels, causing radiative recombination of non-equilibrium carriers, thereby realizing the light emission of high-power LEDs.
[0042] The diamond substrate enhances the thermal conductivity of the device.
[0043] The non-polar GaN buffer layer on the diamond substrate is generally of poor quality. The buffer layer is first grown at a suitable temperature so that the nucleation islands of the buffer layer are large and sparsely distributed, and then the high-temperature growth tends to grow more laterally, which is used to provide nucleation sites for the epitaxial growth of non-polar GaN and improve the crystal quality of the non-polar GaN epitaxial layer.
[0044] The laterally grown periodic n-type AlGaN / GaN layer is formed by etching, regrowth and n-type doping, and the doping concentration is 10 16 -10 18 cm -3 Due to spontaneous polarization and piezoelectric polarization, the laterally alternatingly grown AlGaN / GaN heterojunction produces a high surface density of net bound positive charges at the heterojunction interface, which attracts negatively charged charges and forms multiple two-dimensional electron gas conductive channels, which is equivalent to increasing the carrier concentration of the donor.
[0045] The non-polar Al x Ga 1-x N / A y Ga 1-y The N multi-quantum well layer confines the non-equilibrium carriers in the well layer, where electrons and holes undergo radiation recombination and emit photons. At the same time, the non-polar quantum well eliminates the influence of the quantum confinement Stark effect, greatly improving the luminescence efficiency, so it is the main structure for the device to emit light.
[0046] The laterally grown periodic p-type AlGaN / GaN layer is formed by etching, regrowth and p-type doping, and the doping concentration is 10 17 -10 19 cm -3 Due to spontaneous polarization and piezoelectric polarization, the laterally alternating AlGaN / GaN heterojunction produces a high surface density of net bound negative charges at the heterojunction interface, which attracts positive charges and forms multiple two-dimensional hole gas conduction channels, which is equivalent to increasing the carrier concentration of the acceptor.
[0047] Furthermore, the non-polar GaN buffer layer has a thickness of 3-4 μm.
[0048] Furthermore, the laterally grown periodically alternating n-type AlGaN / GaN heterojunction layer has a thickness of 1-2 μm.
[0049] Furthermore, the non-polar Al x Ga 1-x N / A y Ga 1-y N multi-quantum well layer, the thickness of which is 100-300nm; each period of Al x Ga 1-x N well layer and Al yGa 1-y The thickness of the N barrier layer is 5-10nm and 15-20nm respectively, the adjustment range of Al content x is 0.0-0.5, and the adjustment range of Al content y is 0.1-0.6. The purpose is to set the quantum well emission wavelength to the ultraviolet light band.
[0050] Furthermore, the laterally grown periodically alternating p-type AlGaN / GaN heterojunction layer has a thickness of 1-2 μm.
[0051] Example 1: Prepare an ultraviolet LED with a light emission wavelength of 275 nm.
[0052] Step 1: pre-treating the substrate.
[0053] 1.1) Place the single crystal diamond substrate in a container containing acetone solution and place it in an ultrasonic cleaning device for cleaning for 30 minutes; then take out the cleaned substrate and place it in a drying oven for drying at 70°C;
[0054] 1.2) Soak the dried substrate in a dilute hydrochloric acid solution for 30 minutes, then take out the soaked substrate and put it in a drying oven, and dry it again at 130°C;
[0055] Step 2: growing a non-polar GaN buffer layer, such as Figure 2 (b).
[0056] The MOCVD process was used on a non-polar GaN bulk material substrate. Under the condition of a reaction chamber temperature of 1000°C, ammonia with a flow rate of 3000sccm, gallium source with a flow rate of 180sccm and silicon source with a flow rate of 60sccm were introduced simultaneously. A heavily doped n-type non-polar GaN layer with a thickness of 5μm was grown under the condition of maintaining a pressure of 20Torr, in which the doping concentration of silicon was 10 18 cm -3 .
[0057] Step 3: Etch the non-polar GaN buffer layer, such as Figure 2 (c).
[0058] Using Ni as a mask, an inductively coupled plasma etching process was used on a 5 μm GaN buffer layer. At a reaction chamber temperature of 35°C, chlorine gas with a flow rate of 20 sccm and boron trichloride gas with a flow rate of 8 sccm were introduced at the same time. The number of etching cycles was 10 while maintaining the chamber pressure at 20 Torr, and the thickness of the GaN groove was 1.5 μm.
[0059] Step 4: Laterally grow an n-type AlGaN layer, such as Figure 2 (d).
[0060] The MOCVD process was used on the etched GaN buffer layer at a reaction chamber temperature of 1000°C, while ammonia with a flow rate of 2500sccm, hydrogen with a flow rate of 1200sccm, a gallium source flow rate of 47sccm, an aluminum source flow rate of 150sccm and a silicon source flow rate of 60sccm were introduced.
[0061] Step 5: Growth of Al 0.5 G 0.5 N / A 0.6 G 0.4 N quantum well layers, such as Figure 2 (e).
[0062] Five cycles of Al2O3 were grown on the laterally grown n-type layer using MOCVD at a reaction chamber temperature of 1100°C and a pressure of 45 Torr. 0.5 Ga 0.5 N / A 0.6 Ga 0.4 N quantum wells, each period of a single layer of Al 0.5 Ga 0.5 N well layer and Al 0.6 Ga 0.4 The thickness of the N barrier layer was 5 nm and 15 nm respectively. The flow rate of the nitrogen source was kept at 1100 sccm during the growth process, and the growth of Al 0.5 Ga 0.5 When growing the N-well layer, the gallium source flow rate is kept at 50 sccm and the aluminum source flow rate is kept at 160 sccm. 0.6 Ga 0.4 When forming the N barrier layer, the gallium source flow rate is maintained at 45 sccm and the aluminum source flow rate is maintained at 200 sccm.
[0063] Step 6: grow and etch the p-type GaN layer, such as Figure 2 (f).
[0064] On the multi-quantum well layer, a MOCVD process was used at a reaction chamber temperature of 950°C, while ammonia gas with a flow rate of 2500sccm, hydrogen gas with a flow rate of 1200sccm, gallium source with a flow rate of 150sccm and magnesium source with a flow rate of 100sccm were introduced, and a p-type GaN layer with a thickness of 1μm was grown while maintaining a pressure of 20Torr. Using Ni as a mask, an inductively coupled plasma etching process was used on the 1μm GaN layer at a reaction chamber temperature of 35°C, while chlorine gas with a flow rate of 20sccm and boron trichloride gas with a flow rate of 8sccm were introduced, and the chamber pressure was maintained at 20Torr to etch a GaN groove with a thickness of 1μm and a period number of 10, until the last quantum barrier layer was exposed.
[0065] Step 7: Laterally grow an n-type AlGaN layer, such as Figure 2 (g).
[0066] The MOCVD process is used on the etched p-type GaN layer at a reaction chamber temperature of 1000° C., while introducing ammonia with a flow rate of 2500 sccm, hydrogen with a flow rate of 1200 sccm, a gallium source flow rate of 45 sccm, an aluminum source flow rate of 200 sccm and a Mg source flow rate of 90 sccm.
[0067] Example 2: Prepare an ultraviolet LED with a light emission wavelength of 300 nm.
[0068] Step 1: pre-treating the substrate.
[0069] 1.1) Place the single crystal diamond substrate in a container containing acetone solution and place it in an ultrasonic cleaning device for cleaning for 30 minutes; then take out the cleaned substrate and place it in a drying oven for drying at 80°C;
[0070] 1.2) Soak the dried substrate in a dilute hydrochloric acid solution for 1 hour, then take out the soaked substrate and put it in a drying oven, and dry it again at 150°C;
[0071] Step 2: growing a non-polar GaN buffer layer, such as Figure 2 (b).
[0072] The MOCVD process was used on a non-polar GaN bulk material substrate. Under the condition of a reaction chamber temperature of 1050°C, ammonia with a flow rate of 2500sccm, gallium source with a flow rate of 150sccm and silicon source with a flow rate of 50sccm were introduced simultaneously. A heavily doped n-type non-polar GaN layer with a thickness of 5μm was grown under the condition of maintaining a pressure of 20Torr, in which the doping concentration of silicon was 10 18 cm -3 .
[0073] Step 3: Etch the non-polar GaN buffer layer, such as Figure 2 (c).
[0074] Using Ni as a mask, an inductively coupled plasma etching process is used on a 5 μm GaN buffer layer. At a reaction chamber temperature of 35°C, chlorine gas with a flow rate of 20 sccm and boron trichloride gas with a flow rate of 8 sccm are introduced simultaneously. While maintaining the chamber pressure at 20 Torr, GaN grooves with a thickness of 1.5 μm and a period number of 10 are etched.
[0075] Step 4: Laterally grow an n-type AlGaN layer, such as Figure 2 (d).
[0076] The MOCVD process is used on the etched GaN buffer layer at a reaction chamber temperature of 1050°C, while introducing ammonia with a flow rate of 2300sccm, hydrogen with a flow rate of 1200sccm, a gallium source flow rate of 40sccm, an aluminum source flow rate of 130sccm and a silicon source flow rate of 50sccm.
[0077] Step 5: Growth of Al 0.35 Ga 0.65 N / A 0.55 Ga 0.45 N multiple quantum well structures, such as Figure 2 (e).
[0078] Five cycles of Al growth were performed on the laterally grown n-type layer using MOCVD at a reaction chamber temperature of 1150°C and a pressure of 45 Torr. 0.35 Ga 0.65 N / A 0.55 Ga 0.45 N multiple quantum wells, each period of single layer Al 0.35 Ga 0.65 N well layer and Al 0.55 Ga 0.45 The thickness of the N barrier layer was 6nm and 18nm respectively. The flow rate of the nitrogen source was kept at 1200sccm during the growth process, and the growth of Al 0.35 Ga 0.65 When growing the N-well layer, the gallium source flow rate is kept at 60 sccm and the aluminum source flow rate is kept at 140 sccm. 0.55 Ga 0.45 When forming the N barrier layer, the gallium source flow rate is maintained at 50 sccm and the aluminum source flow rate is maintained at 180 sccm.
[0079] Step 6: grow and etch the p-type GaN layer, such as Figure 2 (f).
[0080] On the multi-quantum well layer, a MOCVD process was used at a reaction chamber temperature of 950°C, while ammonia gas with a flow rate of 2500sccm, hydrogen gas with a flow rate of 1200sccm, gallium source with a flow rate of 150sccm and magnesium source with a flow rate of 100sccm were introduced, and a p-type GaN layer with a thickness of 1μm was grown while maintaining a pressure of 20Torr. Using Ni as a mask, an inductively coupled plasma etching process was used on the 1μm GaN layer at a reaction chamber temperature of 35°C, while chlorine gas with a flow rate of 20sccm and boron trichloride gas with a flow rate of 8sccm were introduced, and the chamber pressure was maintained at 20Torr to etch GaN grooves with a thickness of 1μm and a period number of 10 until the last quantum barrier layer was exposed.
[0081] Step 7, grow an n-type AlGaN layer laterally, such as Figure 2 (g).
[0082] The MOCVD process is used on the etched p-type GaN layer at a reaction chamber temperature of 1050° C., while introducing ammonia with a flow rate of 2500 sccm, hydrogen with a flow rate of 1200 sccm, a gallium source flow rate of 50 sccm, an aluminum source flow rate of 180 sccm and a Mg source flow rate of 80 sccm.
[0083] Example 3: Prepare an ultraviolet LED with a light emission wavelength of 365nm.
[0084] Step 1: pre-treating the substrate.
[0085] 1.1) Place the single crystal diamond substrate in a container containing acetone solution and place it in an ultrasonic cleaning device for cleaning for 30 minutes; then take out the cleaned substrate and place it in a drying oven for drying at 85°C;
[0086] 1.2) Soak the dried substrate in a dilute hydrochloric acid solution for 1.5 hours, then take out the soaked substrate and put it in a drying oven, and dry it again at 160°C;
[0087] Step 2: growing a non-polar GaN buffer layer, such as Figure 2 (b).
[0088] The MOCVD process was used on a non-polar GaN bulk material substrate. Under the condition of a reaction chamber temperature of 950°C, ammonia with a flow rate of 2500sccm, gallium source with a flow rate of 150sccm and silicon source with a flow rate of 60sccm were introduced simultaneously. A heavily doped n-type non-polar GaN layer with a thickness of 5μm was grown under the condition of maintaining a pressure of 20Torr, in which the doping concentration of silicon was 10 19 cm -3 .
[0089] Step 3: Etch the non-polar GaN buffer layer, such as Figure 2 (c).
[0090] Using Ni as a mask, an inductively coupled plasma etching process is adopted on a 5 μm GaN buffer layer. At a reaction chamber temperature of 35°C, chlorine gas with a flow rate of 20 sccm and boron trichloride gas with a flow rate of 8 sccm are introduced simultaneously. While maintaining the chamber pressure at 20 Torr, GaN grooves with a thickness of 1.2 μm and a period number of 5 are etched.
[0091] Step 4: Laterally grow an n-type AlGaN layer, such as Figure 2 (d).
[0092] The MOCVD process was used on the etched GaN buffer layer at a reaction chamber temperature of 1050°C, while ammonia with a flow rate of 2300sccm, hydrogen with a flow rate of 1200sccm, a gallium source flow rate of 50sccm, an aluminum source flow rate of 120sccm and a silicon source flow rate of 50sccm were introduced.
[0093] Step 5: Growth of GaN / Al 0.1 Ga 0.9 N multiple quantum well structures, such as Figure 2 (e).
[0094] Five cycles of GaN / Al were grown on the laterally grown n-type layer using MOCVD at a chamber temperature of 980°C and a pressure of 20 Torr. 0.1 Ga 0.9 N multiple quantum wells, each period has a single layer of GaN well layer and Al 0.1 Ga 0.9 The thickness of the N barrier layer is 5nm and 15nm respectively. During the growth process, the flow rate of the nitrogen source is kept at 1200sccm, and the flow rate of the gallium source is kept at 60sccm when growing the GaN well layer. 0.1 Ga 0.9 When forming the N barrier layer, the gallium source flow rate is maintained at 70 sccm and the aluminum source flow rate is maintained at 140 sccm.
[0095] Step 6: grow and etch the p-type GaN layer, such as Figure 2 (f).
[0096] On the multi-quantum well layer, a MOCVD process was used at a reaction chamber temperature of 950°C, while ammonia gas with a flow rate of 2500sccm, hydrogen gas with a flow rate of 1200sccm, gallium source with a flow rate of 150sccm and magnesium source with a flow rate of 100sccm were introduced, and a p-type GaN layer with a thickness of 1μm was grown while maintaining a pressure of 20Torr. Using Ni as a mask, an inductively coupled plasma etching process was used on the 1μm GaN layer at a reaction chamber temperature of 35°C, while chlorine gas with a flow rate of 20sccm and boron trichloride gas with a flow rate of 8sccm were introduced, and the chamber pressure was maintained at 20Torr to etch GaN grooves with a thickness of 1μm and a period number of 5 until the last quantum barrier layer was exposed.
[0097] Step 7: Laterally grow an n-type AlGaN layer, such as Figure 2 (g).
[0098] The MOCVD process is used on the etched p-type GaN layer at a reaction chamber temperature of 980°C, while introducing ammonia with a flow rate of 2500sccm, hydrogen with a flow rate of 1200sccm, a gallium source flow rate of 70sccm, an aluminum source flow rate of 140sccm and a Mg source flow rate of 60sccm.
[0099] The above descriptions are only three specific examples of the present invention and do not constitute any limitation to the present invention. Obviously, for professionals in this field, after understanding the content and principles of the present invention, it is possible to make various modifications and changes in form and details without departing from the principles and structures of the present invention. However, these modifications and changes based on the ideas of the present invention are still within the scope of protection of the claims of the present invention.
[0100] The present invention proposes a high-power non-polar ultraviolet LED based on a laterally grown AlGaN / GaN heterojunction, which uses a diamond substrate and a periodically laterally grown AlGaN / GaN heterojunction structure in the n-type region and the p-type region to establish multiple conductive channels of two-dimensional electron gas and two-dimensional hole gas, thereby increasing the ionization rate of p-type Mg ions and using a non-polar quantum well to improve device performance. Starting from the overall structure of the device, the present invention provides a method for improving the performance index of the device, which can be used for the preparation of a high-power ultraviolet LED.
Claims
1. A high-power non-polar ultraviolet LED based on a laterally grown AlGaN / GaN heterojunction, comprising a substrate layer, a buffer layer, an n-type region, a multi-quantum well layer and a p-type region from bottom to top, characterized in that: The n-type region is a laterally grown periodic n-type AlGaN / GaN heterojunction, and the p-type region is a laterally grown periodic p-type AlGaN / GaN heterojunction.
2. The high-power non-polar ultraviolet LED based on the laterally grown AlGaN / GaN heterojunction according to claim 1, characterized in that: The substrate layer is diamond, the buffer layer is non-polar GaN, and the non-polar GaN buffer layer on the diamond substrate is used to provide nucleation sites for the epitaxial growth of non-polar GaN and improve the crystal quality of the non-polar GaN epitaxial layer.
3. The high-power non-polar ultraviolet LED based on the laterally grown AlGaN / GaN heterojunction according to claim 1, characterized in that: The laterally grown periodic n-type AlGaN / GaN layer is formed by etching, regrowth and n-type doping, and the doping concentration is 10 16 -10 18 cm -3 Due to spontaneous polarization and piezoelectric polarization, the laterally alternating AlGaN / GaN heterojunction produces a high surface density of net bound positive charges at the heterojunction interface, which attracts negatively charged charges and forms multiple two-dimensional electron gas conductive channels.
4. The high-power non-polar ultraviolet LED based on a laterally grown AlGaN / GaN heterojunction according to claim 1, characterized in that: The multi-quantum well layer is non-polar Al x Ga 1-x N / A y Ga 1-y N, confines the non-equilibrium carriers in the well layer, where electrons and holes undergo radiative recombination and emit photons. At the same time, the non-polar quantum well eliminates the influence of the quantum confinement Stark effect.
5. The high-power non-polar ultraviolet LED based on the laterally grown AlGaN / GaN heterojunction according to claim 4, characterized in that: The non-polar Al x Ga 1-x N / A y Ga 1-y N multi-quantum well layer, the thickness of which is 100-300nm; each period of Al x Ga 1-x N well layer and Al y Ga 1-y The thickness of the N barrier layer is 5-10nm and 15-20nm respectively, the adjustment range of the Al content x is 0.0-0.5, the adjustment range of the Al content y is 0.1-0.6, and the quantum well emission wavelength is set to the ultraviolet light band.
6. The high-power non-polar ultraviolet LED based on a laterally grown AlGaN / GaN heterojunction according to claim 1, characterized in that: The laterally grown periodic p-type AlGaN / GaN layer is formed by etching, regrowth and p-type doping, and the doping concentration is 10 17 -10 19 cm -3 Due to spontaneous polarization and piezoelectric polarization, the laterally alternating AlGaN / GaN heterojunction produces a high surface density of net bound negative charges at the heterojunction interface, which attracts positive charges and forms multiple two-dimensional hole gas conductive channels.
7. The high-power non-polar ultraviolet LED based on a laterally grown AlGaN / GaN heterojunction according to claim 1, characterized in that: The thickness of the non-polar GaN buffer layer is 3-4 μm.
8. The high-power non-polar ultraviolet LED based on a laterally grown AlGaN / GaN heterojunction according to claim 1, characterized in that: The laterally grown periodically alternating n-type AlGaN / GaN heterojunction layer has a thickness of 1-2 μm and a period number of 5-10.
9. The high-power non-polar ultraviolet LED based on a laterally grown AlGaN / GaN heterojunction according to claim 1, characterized in that: The p-type AlGaN / GaN heterojunction layer that is grown laterally and grown periodically and alternately has a thickness of 1-2 μm and a period number of 5-10.
10. A method for preparing a high-power non-polar ultraviolet LED based on a laterally grown AlGaN / GaN heterojunction according to any one of claims 1 to 9, characterized in that: The steps include: 1) Cleaning and drying the substrate; 2) Using MOCVD to grow a GaN buffer layer with a thickness of 4-5 μm; 3) A GaN groove with a thickness of 1-2 μm is etched on the GaN buffer layer by an etching process; 4) Then, an MOCVD process is used to grow AlGaN with the same thickness as the groove on the etched GaN sidewall, forming an AlGaN / GaN heterojunction with a periodic lateral growth of 1-2 μm; 5) Using MOCVD process to grow 5-10 periods of non-polar Al on the laterally grown AlGaN / GaN heterojunction n-type layer x Ga 1-x N / A y Ga 1-y N multi-quantum well layer, Al x Ga 1-x The thickness of the N quantum well is 5-10nm, and the Al y Ga 1-y The thickness of the N quantum barrier is 15-20 nm, the adjustment range of the Al content x is 0.05-0.5, and the adjustment range of the Al content y is 0.15-0.6; 6) growing a 1-2 μm GaN layer on the last quantum barrier layer and etching a GaN groove using an etching process until the last quantum barrier layer is exposed; 7) Grow a laterally grown periodic p-type AlGaN / GaN layer. Use the MOCVD process to grow AlGaN with the same thickness as the groove on the etched GaN sidewall, forming a periodically laterally grown AlGaN / GaN heterojunction as the p-type region of the device, and obtaining a high-power non-polar ultraviolet LED.