Epitaxial wafer of high-luminous-efficiency infrared light-emitting diode and manufacturing method of epitaxial wafer

Abstract

The invention provides an epitaxial wafer of a high-luminous-efficiency infrared light-emitting diode and a manufacturing method of the epitaxial wafer. The epitaxial wafer comprises a GaAs substrate, an N-type semiconductor structure, a quantum well active region and a P-type semiconductor structure, wherein the N-type semiconductor structure, the quantum well active region and the P-type semiconductor structure are formed on the substrate. The N-type semiconductor structure comprises an N-type AlGaAs stacking layer, diethyl tellurium (DETe) and disilane (Si2H6) are adopted for co-doping, the N-type semiconductor structure is designed to be of a superlattice structure, and the doping concentration in the vertical direction is periodically alternated from high to low; and a doping concentration gradient is arranged at a position close to the quantum well region, so that the tellurium doping concentration is gradually increased. Through the design, the content of carbon impurities in the material and the non-radiative recombination probability are reduced, a better current expansion effect and quantum well stress release are achieved, and the luminous efficiency and performance of an infrared LED are greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of light emitting diode (LED) semiconductor technology, and in particular to an epitaxial wafer of a high-light-efficiency infrared light emitting diode and a manufacturing method thereof. Background Art

[0002] Infrared light-emitting diodes (IDs) are semiconductor devices that emit near-infrared light, typically with a wavelength in the 0.70μm to 1.0μm range. Due to their compact size, low power consumption, long life, high stability, and excellent directivity, these LEDs are widely used in areas such as camera-assisted lighting, material composition analysis, remote sensing, biomedicine, and plant photography. With the emergence of emerging demands such as 5G / 6G communications, autonomous driving, and precision medicine, the application prospects of infrared LEDs are even broader. However, improving the luminous efficiency of infrared LEDs has always been a key technical concern and a challenge for the industry.

[0003] Conventional infrared light-emitting diode epitaxial structures such as Figure 1 As shown, it includes: a substrate, and an N-type GaAs buffer layer, an N-type GaInP etching stop layer, an N-type GaAs ohmic contact layer, an N-type AlGaAs extension layer, an N-type AlGaAs confinement layer, a quantum well active layer, a P-type AlGaAs confinement layer, a P-type AlGaAs window layer, a P-type GaInP transition layer and a P-type GaP ohmic contact layer grown in sequence on the substrate. In conventional epitaxial growth processes, the above-mentioned N-type AlGaAs extension layer and N-type AlGaAs confinement layer usually serve as a current spreading layer and a carrier confinement layer, respectively, and their N-type doping generally uses diethyltellurium (DETe) or disilane (Si2H6) as a doping source. However, this traditional single doping method has many shortcomings and is difficult to significantly improve the luminous efficiency of infrared LEDs. For example, when only DETe is used as the N-type doping source, due to the large atomic radius of the tellurium element, it may introduce higher lattice stress and defect density in the AlGaAs crystal, reducing the material quality and being detrimental to the luminous efficiency. In addition, DETe doping will lead to an increase in the carbon (C) impurity content in the AlGaAs material, and an excessive amount of Group V source gases such as AsH3 need to be introduced to suppress carbon impurities, which increases the growth cost. When only Si2H6 is used as the N-type doping source, silicon doping is prone to form deep energy level trap centers, increasing the probability of non-radiative recombination, thereby reducing the carrier recombination luminescence efficiency and significantly affecting the carrier lifetime and device performance. In summary, the pure Te doping or pure Si doping schemes in the existing technology have limitations and cannot achieve further breakthroughs in luminescence efficiency in infrared LED epitaxial structures. Summary of the Invention

[0004] In response to the above-mentioned deficiencies in the prior art, the present invention proposes an optimized infrared light-emitting diode epitaxial wafer structure and a growth method thereof, so as to significantly improve the luminous efficiency of infrared LEDs by improving the doping strategy of the N-type layer without changing the material system.

[0005] The high-efficiency infrared light-emitting diode epitaxial wafer of the present invention includes a GaAs substrate, an N-type semiconductor layer structure, a quantum well active layer, and a P-type semiconductor layer structure. The N-type semiconductor layer structure includes multiple layers of arsenide material, the core of which is an N-type AlGaAs stacked layer. The N-type AlGaAs stacked layer consists of two adjacent parts: a first N-type AlGaAs layer located below (on the side close to the N-type GaAs ohmic contact layer) and a second N-type AlGaAs layer located above (on the side close to the quantum well active layer). Both parts are co-doped with DETe and Si2H6, but the doping profiles are different.

[0006] In the first N-type AlGaAs layer, a superlattice doping structure design is adopted, that is, by adjusting the supply of DETe doping source, a high-doping region and a low-doping region that periodically alternate along the growth direction are formed in the layer (that is, the DETe concentration alternates between high and low values), and at the same time, an appropriate amount of Si2H6 is introduced to provide background n-type doping. Through this high-low doping concentration alternating design, different carrier concentration distributions can be achieved at different positions of the AlGaAs layer, thereby enhancing the lateral current expansion capability. Under the premise of satisfying current diffusion, the thickness of the first N-type AlGaAs layer can be appropriately reduced to reduce the material's own absorption loss of luminescence.

[0007] In the second N-type AlGaAs layer, a doping gradient design is adopted, that is, a higher concentration of DETe doping is introduced on the side close to the quantum well, while a lower DETe doping concentration is maintained on the side away from the quantum well, so that the concentration of DETe gradually increases along the growth direction. Si2H6 also provides N-type co-doping in this layer, but the concentration is relatively low and remains basically constant. By increasing the Te doping concentration near the quantum well, on the one hand, more electron carriers can be gathered near the active area, thereby increasing the probability of radiative recombination; on the other hand, due to the large mass and radius of Te atoms, higher Te doping will introduce a slight lattice constant change in the area adjacent to the quantum well, which plays a role in releasing quantum well stress, thereby helping to stabilize the quantum well structure and improve luminous efficiency.

[0008] In addition, the quantum well active layer of the present invention is preferably a multi-quantum well structure, for example, several pairs are alternately formed by InGaAs quantum wells and AlGaAsP barriers to achieve the required luminescence wavelength and intensity. The P-type semiconductor layer structure can adopt a conventional design, for example, including a P-type AlGaAs confinement layer (electron blocking layer) adjacent to the quantum well, a thicker P-type AlGaAs window layer (to reduce surface recombination and absorption losses), a P-type GaInP transition layer and a top-most P-type GaP contact layer. Among them, P-type doping can use an organic magnesium source (Cp2Mg) or a halide carbon source (CBr4, CCl4) to achieve high-concentration hole-type doping. Through the above-mentioned structural design, the epitaxial wafer of the present invention focuses on improving the doping distribution of the N-type layer while maintaining the compatibility of the original material system, thereby improving the performance of the overall device.

[0009] Compared with the existing infrared LED epitaxial structure, the present invention has significant beneficial effects. First, through the co-doping of DETe+Si2H6, the carbon impurity content in the AlGaAs material is effectively reduced, and the background carbon level can be controlled without the need for additional large amounts of arsine (AsH3), thereby simplifying the process and reducing production costs. At the same time, the introduction of Si improves the ionization activation rate of N-type impurities and reduces the generation of deep energy level defect centers. The synergistic effect of the two impurities improves the crystal quality and carrier transport characteristics of the material. Secondly, the superlattice doping design in the first N-type AlGaAs layer makes the lateral diffusion of carriers more uniform, effectively reducing the local luminous efficiency drop caused by current crowding, and allowing the thickness of the layer to be thinned to reduce the absorption loss of infrared light in the N-type layer. Thirdly, the doping gradient design in the second N-type AlGaAs layer relaxes the stress of the quantum well and improves the quantum efficiency. These improvements work together to improve the light output power and electrical performance of the infrared LED. According to test results, under the conditions of a wavelength of approximately 850nm, a chip size of 42mil, and an injection current of 350mA, the epitaxial wafer of the present invention reduces the forward voltage of the LED from approximately 1.62V to approximately 1.60V compared to the conventional structure. At the same time, the output optical power at the same drive current is increased from approximately 385mW to approximately 405mW, an improvement of more than 5%. This shows that through material doping and structural innovation, the present invention significantly improves the luminous efficiency and output power of infrared light-emitting diodes, providing reliable technical support for the high-performance application of infrared LEDs in night vision monitoring, communications, medical treatment and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 A schematic diagram of an infrared light-emitting diode epitaxial structure in the prior art;

[0011] Figure 2 This is a schematic diagram of the structure of the high-efficiency infrared light-emitting diode epitaxial wafer provided by the present invention. Figure 1The labels of the layers are as follows: 500 is a GaAs substrate; 501 is an N-type GaAs buffer layer; 100 is an N-type GaInP etching stop layer; 101 is an N-type GaAs ohmic contact layer; 102 is an N-type AlGaAs extension layer; 103 is an N-type AlGaAs confinement layer, 104 is a multiple quantum well, 105 is a P-type AlGaAs confinement layer, 106 is a P-type AlGaAs window layer, 107 is a P-type GaInP transition layer, and 108 is a P-type GaP ohmic contact layer; in Figure 2 The layers are numbered as follows: 600 is a GaAs substrate; 601 is an N-type GaAs buffer layer; 200 is an N-type GaInP etching stop layer; 201 is an N-type GaAs ohmic contact layer; 202 is a first N-type AlGaAs layer; 203 is a second N-type AlGaAs layer; 204 is a multi-quantum well active layer; 205 is a P-type AlGaAs confinement layer; 206 is a P-type AlGaAs window layer; 207 is a P-type GaInP transition layer; and 208 is a P-type GaP ohmic contact layer. The thickness ratios of the layers in the figure are not drawn to scale and are only used to illustrate the structure of the present invention. DETAILED DESCRIPTION

[0012] The epitaxial structure and the manufacturing method thereof of the present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the present invention is not limited to these embodiments.

[0013] like Figure 2 As shown, a high-light-efficiency infrared light-emitting diode epitaxial wafer provided in this embodiment includes, from bottom to top, a GaAs substrate (600), an N-type GaAs buffer layer (601), an N-type GaInP etching stop layer (200), an N-type GaAs ohmic contact layer (201), a first N-type AlGaAs layer (202), a second N-type AlGaAs layer (203), a multi-quantum well active layer (204), a P-type AlGaAs confinement layer (205), a P-type AlGaAs window layer (206), a P-type GaInP transition layer (207), and a topmost P-type GaP ohmic contact layer (208). The material composition, doping, and growth conditions of each layer are described in detail below.

[0014] N-type layer growth: On a clean GaAs substrate (600), an N-type GaAs buffer layer (601) is first grown by MOCVD. The growth temperature is controlled at approximately 700°C (preferably in the range of 680-740°C) to ensure crystal quality. Arsenic is provided by arsine (AsH3) and gallium is provided by trimethylgallium (TMGa) as a gas source. A small amount of disilane (Si2H6) is introduced as an n-type doping source to achieve a buffer layer doping concentration of approximately 1×10 18 ~3×10 18 carriers·cm -3(Silicon is a donor impurity). The thickness of the GaAs buffer layer is approximately (scope ).

[0015] Next, an N-type GaInP etching stop layer (200) is grown on the buffer layer, and a GaInP alloy is grown using pentaalkyl gallium (TMGa), pentaalkyl indium (TMIn) and phosphine (PH3). The growth temperature can be the same as that of the previous layer or slightly adjusted (about 680-700°C). Si2H6 is also used to dope the GaInP layer to 1×10 18 ~3×10 18 carriers·cm -3 The n-type concentration is to ensure that the layer has conductivity in the subsequent device process and can serve as a stop layer for selective etching. The thickness of the GaInP layer is about (scope ).

[0016] An N-type GaAs ohmic contact layer (201) is grown on the GaInP layer. GaAs is grown by continuing to introduce TMGa and AsH3, while increasing the flow of Si2H6 to achieve heavily doped n-type GaAs. The doping concentration is controlled to be greater than 5×10 18 carriers·cm -3 , to form a highly doped contact layer, thereby reducing the contact resistance between the N electrode and the N-type layer. The growth temperature of this layer is about 700℃ and the thickness is about (scope ).

[0017] Next, an N-type AlGaAs stacked layer is grown according to the key scheme of the present invention. First, a first N-type AlGaAs layer (202) is grown. TMGa, TMAl, and AsH3 are introduced to co-deposit an AlGaAs alloy, wherein the Al component ratio is controlled to be about 20% (range 15% to 25%). DETe and Si2H6 are introduced simultaneously as n-type doping sources during the entire AlGaAs growth process to achieve co-doping of Te and Si. By adjusting the supply amount of the DETe source, the first N-type AlGaAs layer forms a superlattice doping structure in the growth direction - that is, whenever it grows to a certain thickness (for example, The DETe supply is appropriately reduced to form a low-doped layer segment, and then the DETe supply is increased to form a high-doped layer segment, and this is repeated alternately, so that the thickness of the layer is 6 to 8 μm. Several pairs of high / low doping sublayers are formed in the AlGaAs layer. Preferably, the carrier concentration of DETe in the high doping section is about 3×10 17 ~5×10 17 carriers·cm -3, the corresponding carrier concentration in the low-doping section is about 1×10 17 ~2×10 17 carriers·cm -3 The doping concentration of Si2H3 in the entire first AlGaAs layer can be maintained at about 1×10 17 ~3×10 17 carriers·cm -3 Through the above-mentioned superlattice co-doping design, the carrier distribution and current spreading effect can be significantly optimized, and the absorption of luminescence by the thick AlGaAs layer can be reduced.

[0018] Then, the second N-type AlGaAs layer (203) is grown, and its Al content is slightly higher, controlled at about 30% (range 25% to 35%), so as to form a certain barrier to the quantum well in the energy band (limiting the electrons from overflowing into the N region). The thickness of this layer is relatively thin, about (scope ). DETe and Si2H+ are continued to be co-doped, but the periodic alternation is no longer used. Instead, the doping concentration of DETe is gradually increased along the growth direction: the concentration is maintained at about 5×10 near the junction of the first AlGaAs layer below. 17 ~6×10 17 carriers·cm -3 The Te doping level is adjusted by gradually increasing the DETe supply so that the Te doping concentration near the quantum well layer (204) increases to about 7×10 17 ~8×10 17 carriers·cm -3 The doping concentration of Si2H+ in the second AlGaAs layer is still controlled at about 1×10 17 ~3×10 17 carriers·cm -3 Through this gradual doping design, the second AlGaAs layer has a higher electron concentration and a slightly larger lattice constant near the active region, which helps reduce non-radiative recombination caused by stress in the quantum well, thereby improving quantum efficiency.

[0019] Active region growth: After the above-mentioned N-type layer structure is completed, stop introducing any doping source and grow a multi-quantum well active layer (204) on the second AlGaAs layer. For example, InGaAs quantum well layers and AlGaAsP barrier layers can be grown alternately to form a light-emitting active region. In this embodiment, each quantum well structure consists of a thickness of about The InGaAs well layer has a thickness of about The AlGaAsP barrier layer consists of an Al composition of approximately 0.1 and a P composition of approximately 0.1. Preferably, the number of quantum well pairs is 8 (with an optional range of 4 to 15 pairs) to balance luminescence intensity and material stress. The active region remains undoped throughout the growth process to prevent impurities from affecting radiative recombination.

[0020] P-type layer growth: After the active area is completed, the P-type semiconductor layer structure is grown on it. First, the P-type AlGaAs confinement layer (205) is grown. The Al content of this layer is about 30% (25% to 35%) and the thickness is about 10%. The main function is to act as an electron blocking layer to limit the overflow of carriers in the active area. During the growth process, Cp2Mg (organic magnesium source) or halocarbon source (CBr4, CCl4) is introduced for P-type doping, so that the hole concentration of this layer reaches about 1×10 18 carriers·cm -3 About (typical range 9×10 17 ~1.5×10 18 carriers·cm -3 ).

[0021] Then grow a P-type AlGaAs window layer (206), reduce the Al content to about 20% (15% to 25%), and increase the thickness to about 2μm The function of the window layer is to widen the light emission window and reduce surface recombination. This layer is also doped with Mg or C sources, and the concentration is controlled at about 1×10 18 ~2×10 18 carriers·cm -3 , making it have good electrical conductivity.

[0022] Then grow a P-type GaInP transition layer (207) with a thickness of about Since GaInP material has a large energy band and has a lattice matching effect with GaP, the introduction of this transition layer can improve the P-type contact characteristics. This layer is doped with Mg source (Cp2Mg) to achieve p-type doping with a concentration of about 2×10 18 ~3×10 18 carriers·cm -3 .

[0023] Finally, a P-type GaP ohmic contact layer (208) is grown with a thickness of about GaP has a high energy gap and good surface stability, which can improve the transparency of the surface area and serve as a low-resistance contact layer for metal electrodes. By doping with high concentrations of CBr4 or CCl4, the hole concentration can be increased to >5×10 19 carriers·cm -3, ensuring the formation of good P-type ohmic contact.

[0024] At this point, the entire infrared light emitting diode epitaxial structure is grown according to the design of the present invention. The resulting epitaxial wafer structure is as follows: Figure 2 After conventional chip preparation processes (such as photolithography, electrode evaporation, dicing and packaging), LED devices were made and tested. The test results are shown in the following table:

[0025]

[0026] Tests show that the infrared LED of the present invention exhibits lower forward voltage drop and higher output optical power while maintaining stable operation, offering significant advantages over conventional structures in the prior art. Through innovative design at the material structure level, the present invention improves the optoelectronic performance of infrared LEDs and has promising prospects for industrial application.

Claims

1. An epitaxial wafer for a high-efficiency infrared light-emitting diode, comprising a GaAs substrate, an N-type semiconductor structure, a quantum well active region, and a P-type semiconductor structure sequentially formed on the substrate, characterized in that: The N-type semiconductor structure includes an N-type AlGaAs stacked layer, which is composed of a first N-type AlGaAs layer and a second N-type AlGaAs layer adjacent to the first N-type AlGaAs layer; wherein the first N-type AlGaAs layer is co-doped with diethyltellurium (DETe) and disilane (Si2H6) and grown in the form of a superlattice structure, and the DETe doping concentration in the first N-type AlGaAs layer is periodically distributed alternating between high and low concentrations along the growth direction; the second N-type AlGaAs layer is co-doped with DETe and Si2H6 and has a gradually increasing DETe doping concentration gradient on the side close to the quantum well active region.

2. The epitaxial wafer according to claim 1, wherein: The Al element mole fraction of the first N-type AlGaAs layer is 0.15-0.25, and the thickness is When growing the first N-type AlGaAs layer, DETe and Si2H6 are introduced for co-doping; wherein the doping concentration of Si2H6 is 1×10 17 ~3×10 17 carriers·cm -3 , the low-concentration doping concentration of DETe is 1×10 17 ~2×10 17 carriers·cm -3 , the high concentration doping concentration is 3×10 17 ~5×10 17 carriers·cm -3 .

3. The epitaxial wafer according to claim 1, wherein: The Al element mole fraction of the second N-type AlGaAs layer is 0.25-0.35, and the thickness is When growing the second N-type AlGaAs layer, DETe and Si2H6 are introduced for co-doping, and the doping concentration of DETe is increased from 5×10 17 ~6×10 17 carriers·cm -3 Gradually increases to 7×10 near the active region of the quantum well 17 ~8×10 17 carriers·cm -3 The doping concentration of Si2H6 is 1×10 17 ~3×10 17 carriers·cm -3 .

4. The epitaxial wafer according to claim 1, wherein: The DETe high-concentration doping region and the low-concentration doping region of the first N-type AlGaAs layer alternately form a superlattice structure, and the superlattice period of high and low doping concentrations is repeated 10 to 30 pairs in the first N-type AlGaAs layer.

5. The epitaxial wafer according to claim 1, wherein: The quantum well active region is a multi-quantum well structure, which is composed of InGaAs quantum well layers and AlGaAsP barrier layers alternately. The thickness of the quantum well layer is The thickness of the barrier layer is The molar fraction of Al element is 0.05-0.15, the molar fraction of P element is 0.08-0.15, the number of quantum well pairs is 4-15 pairs, and the active region is an intrinsic layer without doping.

6. The method for manufacturing an epitaxial wafer according to any one of claims 1 to 5, characterized in that: The metal organic chemical vapor deposition (MOCVD) process is used to grow each layer structure at a reaction chamber temperature of 680 to 740°C, including the following steps: Step 1, epitaxially growing an N-type GaAs buffer layer, an N-type GaInP etching stop layer and an N-type GaAs ohmic contact layer on a GaAs substrate in sequence, wherein Si2H6 gas is introduced into each layer as an N-type doping source during growth; Step 2, continuing the epitaxial growth of the N-type AlGaAs stacked layer, including sequentially growing the first N-type AlGaAs layer and the second N-type AlGaAs layer, and simultaneously introducing DETe and Si2H6 gas during the growth process for N-type co-doping, wherein during the growth process of the first N-type AlGaAs layer, the doping concentration of DETe is controlled to alternately change in a high-low-high-low cycle to form a superlattice doping structure, and during the growth process of the second N-type AlGaAs layer, the doping concentration of DETe is controlled to gradually increase along the growth direction; Step 3, epitaxially growing the quantum well active region, which is an InGaAs / AlGaAsP multi-quantum well structure without introducing doping; Step 4, epitaxially growing a P-type semiconductor structure, including sequentially growing a P-type AlGaAs confinement layer, P-type AlGaAs window layer, P-type GaInP transition layer and P A GaP ohmic contact layer is formed, and a P-type doping source is introduced during the growth process, wherein the P-type doping source is selected from bismuth magnesium (Cp2Mg), carbon tetrabromide (CBr4) or carbon tetrachloride (CCl4).

7. The production method according to claim 6, characterized in that: In step 1, the thickness of the N-type GaAs buffer layer and the N-type GaInP etching stop layer are both The doping concentration is 1×10 18 ~3×10 18 carriers·cm -3 ; The thickness of the N-type GaAs ohmic contact layer is Doping concentration is greater than 5×10 18 carriers·cm -3 .

8. The production method according to claim 6, characterized in that: In step 4, the Al element mole fraction of the P-type AlGaAs confinement layer is 0.25-0.35, and the thickness is The doping concentration is 9×10 17 ~1.5×10 18 carriers·cm -3 The Al element mole fraction of the P-type AlGaAs window layer is 0.15 to 0.25, and the thickness is The doping concentration is 1×10 18 ~2×10 18 carriers·cm -3 ; The thickness of the P-type GaInP transition layer is The doping concentration is 2×10 18 ~3×10 18 carriers·cm -3 ; The thickness of the P-type GaP ohmic contact layer is Doping concentration is greater than 5×10 19 carriers·cm -3 .

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