Epitaxial structure for optimizing ESD and preparation method

Abstract

The invention relates to an ESD-optimized epitaxial structure and a preparation method thereof, and belongs to the technical field of light-emitting diodes. A buffer, a DBR Bragg reflector, an N-type limiting layer, an N-type barrier layer, an active light-emitting layer, a P-type barrier layer, a P-type limiting layer and a P-type current expansion Gap (including a low-temperature low-speed layer and a gradient high-temperature high-speed layer) are grown on a substrate in sequence; according to the invention, for the design of the Gap layer, the growth quality of the Gap can be improved to the maximum extent through precise control of the growth speed and the growth temperature, and then the Mg doping level in the Gap is improved under the condition that the III doping proportion is not changed, so that the ESD performance of the epitaxial wafer is improved.

Description

Technical Field

[0001] The invention relates to an epitaxial structure for optimizing ESD and a preparation method thereof, belonging to the technical field of light emitting diodes. Background Art

[0002] Light Emitting Diode (LED) is a semiconductor electronic component that can emit light. In recent years, LED has been widely used due to its advantages such as low power consumption, long life, small size, energy saving and environmental protection. For example, it can be used in indoor and outdoor lighting, traffic lights, backlight sources and other fields.

[0003] Red light diode is an important light source device, widely used in outdoor lighting and automobile taillights. Red light diode chip is the basic structure for preparing red light diode. Among them, epitaxial structure plays the most important role as the front process of red light diode. Conventional red light epitaxial structure usually includes substrate and DBR, n-type AlInP confinement layer, n-type barrier layer, light-emitting layer, p-type barrier layer, p-type AlInP confinement layer, p-type GaP current expansion layer and other structures stacked on the substrate in sequence. With the long-term occupation of the market, its process structure has gradually become unified, and the basic parameters of each company have reached the market stable level. However, as the size gradually decreases, the parameter requirements are also constantly increasing. In recent years, in the display field, ESD parameters are particularly important and prominent. This paper optimizes the current expansion layer growth method through Gap, improves the growth quality of Gap layer, and improves the Mg doping level of Gap, thereby improving the ESD performance of epitaxial wafers to solve the above technical problems in the industry. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides an epitaxial structure and growth method for optimizing ESD, which sequentially grow a buffer, a DBR Bragg reflector, an N-type confinement layer, an N-type barrier layer, an active light-emitting layer, a P-type barrier layer, a P-type confinement layer, and a P-type current expansion Gap (including a low-temperature and low-speed layer and a gradient high-temperature and high-speed layer) on a substrate; wherein the invention of this article is the design of the Gap layer, which can maximize the growth quality of the Gap through precise control of the growth rate and the growth temperature, and then improve the Mg doping level in the Gap without changing the III doping ratio, thereby improving the ESD performance of the epitaxial wafer.

[0005] The technical solution of the present invention is as follows:

[0006] An epitaxial structure for optimizing ESD includes a substrate, on which a buffer layer, a DBR layer, an N-type limiting layer, an N-type blocking layer, an active layer, a P-type blocking layer, a P-type limiting layer and a P-type current spreading layer are sequentially arranged from bottom to top;

[0007] The P-type current extension layer is a Gap layer, which includes a low-temperature and low-speed layer and a high-temperature and high-speed layer from bottom to top. The Mg doping concentration in the low-temperature and low-speed layer is consistent, and the Mg doping concentration in the high-temperature and high-speed layer gradually increases. The Mg doping starting concentration of the high-temperature and high-speed layer is consistent with the Mg doping concentration in the low-temperature and low-speed layer.

[0008] Preferably, the Mg doping concentration of the low-temperature and low-speed layer is 0.5-2E+18atom / cm3; the Mg doping concentration of the high-temperature and high-speed layer is 2-5E+18atom / cm3.

[0009] Preferably, the Mg doping concentration of the high-temperature and high-speed layer increases gradually in a linear manner.

[0010] In this case, the ESD performance is optimized through the two-layer process design of the current spreading layer.

[0011] Preferably, according to the present invention, the epitaxial structure for optimizing ESD includes one of the following solutions (1)-(7):

[0012] (1) The buffer layer is a GaAs layer with a thickness of 0.5-0.8 μm;

[0013] (2) The DBR layer is a periodic structure in which AlAs layers and AlGaAs layers are arranged alternately. The thickness of each AlAs layer is 550A and the thickness of the AlGaAs layer is 500A. The AlAs layers and AlGaAs layers are arranged alternately 14 times, with a total of 28 layers.

[0014] (3) The N-type limiting layer is an AIP layer with a thickness of 3000A;

[0015] (4) N-type barrier layer is (Al a Ga 1-a ) 0.5 In 0.5 P layer, thickness is 1000A, 0.3≤a≤0.4;

[0016] (5) The active layer is a periodic structure in which well layers and barrier layers are alternately arranged, the well layers are GaInP, and the barrier layers are AlGaInP; one well layer and barrier layer constitute one period, the number of periods is 10-20, and the thickness of the active layer is 0.15 μm-0.2 μm;

[0017] (6) The P-type barrier layer is (Al a Ga 1-a ) 0.5 In 0.5 P layer, thickness is 1000A, 0.3≤a≤0.4;

[0018] (7) The P-type limiting layer is an AIP layer with a thickness of 3000A.

[0019] Preferably, the thickness of the P-type current spreading layer is 4 um, wherein the first 1 um is a low-temperature and low-speed layer; and the last 3 um is a gradient high-temperature and high-speed layer.

[0020] A method for preparing an epitaxial structure for optimizing ESD, comprising the following steps:

[0021] S1: placing the substrate into a reaction chamber of a metal organic chemical vapor deposition device, and sequentially growing a buffer layer, a DBR layer, an N-type restriction layer and an N-type barrier layer on the substrate;

[0022] S2: growing an active layer on the N-type barrier layer;

[0023] S3: growing a P-type barrier layer and a P-type confinement layer on the active layer;

[0024] S4: growing a P-type current spreading layer on the P-type limiting layer, and growing a low-temperature and low-speed layer and a high-temperature and high-speed layer through process control.

[0025] Preferably, according to the present invention, in step S1, the buffer layer growth process is specifically as follows:

[0026] Set the reaction chamber pressure to 50-60 mbar and the temperature to 700-800°C, and introduce 100-120 sccm of TMGa into the reaction chamber for 4-6 minutes to grow a buffer layer;

[0027] The specific process of DBR layer growth is as follows:

[0028] The reaction chamber pressure is set to 50-60 mbar and the temperature is set to 700-800° C. At the same time, 300-500 sccm of AsH3 and 400-800 sccm of TMAl are introduced into the reaction chamber to grow an AlAs layer, and then 400-800 sccm of TMAl and 100-200 sccm of TMGa are introduced to grow an AlGaAs layer. The growth is alternating for 30-60 minutes to form a DBR layer on the buffer layer.

[0029] The specific growth process of the N-type confinement layer is as follows:

[0030] Close the AsH3 channel, and introduce 800-1200sccm of PH3, 300-500sccm of TMIn and 150-200sccm of TMAl into the reaction chamber. The doping concentration of Si is 1-3E+18atom / cm 3 , lasting 5-15 minutes, forming an N-type restriction layer;

[0031] The specific process of N-type barrier layer growth is as follows:

[0032] Maintaining the PH3 atmosphere, the designed flow rates of 300-500 sccmTMIn, 150-200 TMAl, and 30-40 sccmTMGa are introduced for 2-5 minutes to form an N-type barrier layer on the N-type restriction layer.

[0033] Preferably, according to the present invention, in step S2, the active layer growth process is specifically as follows:

[0034] Maintaining the PH3 atmosphere for 10-20 minutes, alternately growing the well layer and the barrier layer of the multi-quantum well active layer; the well layer is GaInP, and the barrier layer is AlGaInP; each growth of the well layer and the barrier layer is a cycle, and the number of GaInP / AlGaInP cycles is 10 to 20; forming an active layer.

[0035] Preferably, according to the present invention, in step S3, the P-type barrier layer growth process is specifically as follows:

[0036] After the active layer is grown, the temperature of the reaction chamber is set to 700-800°C, the pH is maintained at 3, and the designed flow rates of 300-500 sccmTMIn, 150-200 sccmTMAl, and 30-40 sccmTMGa are introduced for 2-5 minutes to form an N-type barrier layer;

[0037] The specific growth process of the P-type confinement layer is as follows:

[0038] Set the reaction chamber temperature to 700-800°C and the pressure to 50-60mbar, introduce 800-1200sccm of PH3, 300-500sccm of TMIn and 150-200sccm of TMAl into the reaction chamber, and the Mg doping concentration to 1-3E+18atom / cm3 for 5-15 minutes to form a P-type confinement layer.

[0039] Preferably, according to the present invention, in step S4, the growth process of the P-type current spreading layer is specifically as follows:

[0040] Set the reaction chamber temperature to 700-800°C and the pressure to 50-60mbar, introduce 200-400sccm of PH3 and 50-100sccm of TMGa into the reaction chamber; the Mg doping concentration is 0.5-2E+18atom / cm3, and continue for 20-30 minutes to form a low-temperature and low-speed layer;

[0041] The reaction chamber temperature is set at 800-1000°C and the pressure is set at 50-60mbar. 400-800sccm of PH3 and 300-500sccm of TMGa are introduced into the reaction chamber. The doping concentration of Mg is 2-5E+18atom / cm3 for 20-30 minutes to form a gradual high-temperature and high-speed layer.

[0042] The beneficial effects of the present invention are:

[0043] For the design of the Gap layer, high-level Mg doping plays an important positive role in the ESD performance, but simply increasing the Mg dosage will make the Gap surface growth worse and the optical parameters will also decrease accordingly; this paper improves the growth quality by precisely controlling the temperature and growth rate levels, and without increasing the Mg dosage, the P-type current spreading layer can form a higher concentration of doping level, thereby having a higher carrier concentration, which significantly improves the ESD resistance of the light-emitting diode. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a diagram illustrating the preparation steps of the present invention;

[0045] Figure 2 It is a structural schematic diagram of the present invention;

[0046] Figure 3 It is a diagram to distinguish between the embodiment of the present invention and the comparative example. DETAILED DESCRIPTION

[0047] The present invention will be further described below by way of embodiments in conjunction with the accompanying drawings, but is not limited thereto.

[0048] Embodiment 1:

[0049] An epitaxial structure for optimizing ESD includes a substrate, on which a buffer layer, a DBR layer, an N-type limiting layer, an N-type blocking layer, an active layer, a P-type blocking layer, a P-type limiting layer and a P-type current expansion layer are sequentially arranged from bottom to top.

[0050] The P-type current extension layer is a Gap layer, which includes a low-temperature and low-speed layer and a high-temperature and high-speed layer from bottom to top. The Mg doping concentration in the low-temperature and low-speed layer is consistent, and the Mg doping concentration in the high-temperature and high-speed layer gradually increases. The Mg doping starting concentration of the high-temperature and high-speed layer is consistent with the Mg doping concentration in the low-temperature and low-speed layer.

[0051] The Mg doping concentration of the low temperature and low speed layer is 0.5-2E+18atom / cm3; the Mg doping concentration of the high temperature and high speed layer is 2-5E+18atom / cm3. The Mg doping concentration of the high temperature and high speed layer increases linearly.

[0052] The buffer layer is a GaAs layer with a thickness of 0.5-0.8μm; the DBR layer is a periodic structure of alternating AlAs layers and AlGaAs layers, each AlAs layer is 550A thick and the AlGaAs layer is 500A thick; the AlAs layer and the AlGaAs layer are alternately arranged 14 times, with a total of 28 layers; the N-type limiting layer is an AIP layer with a thickness of 3000A; the N-type barrier layer is (Al a Ga1-a ) 0.5 In 0.5 P layer, thickness is 1000A, 0.3≤a≤0.4; the active layer is a periodic structure of well layers and barrier layers arranged alternately, the well layers are GaInP, and the barrier layers are AlGaInP; one well layer and barrier layer is one period, the number of periods is 10-20, and the thickness of the active layer is 0.15μm-0.2μm; the P-type barrier layer is (Al a Ga 1-a ) 0.5 In 0.5 P layer, thickness is 1000A, 0.3≤a≤0.4; P-type limiting layer is AIP layer, thickness is 3000A.

[0053] The thickness of the P-type current spreading layer is 4um, of which the first 1um is a low-temperature and low-speed layer; the last 3um is a gradient high-temperature and high-speed layer.

[0054] Embodiment 2:

[0055] An epitaxial structure for optimizing ESD, the structure of which is as described in Example 1, except that the Mg doping concentration of the low-temperature and low-speed layer is 0.5E+18atom / cm3; the Mg doping concentration of the high-temperature and high-speed layer is 2E+18atom / cm3. The Mg doping concentration of the high-temperature and high-speed layer increases linearly.

[0056] The buffer layer is a GaAs layer with a thickness of 0.5μm; the DBR layer is a periodic structure of alternating AlAs layers and AlGaAs layers, each AlAs layer is 550A thick and the AlGaAs layer is 500A thick; the AlAs layer and the AlGaAs layer are alternately arranged 14 times, with a total of 28 layers; the N-type limiting layer is an AIP layer with a thickness of 3000A; the N-type barrier layer is (Al a Ga 1-a ) 0.5 In 0.5 P layer, thickness is 1000A, a=0.3; the active layer is a periodic structure of well layers and barrier layers arranged alternately, the well layers are GaInP, and the barrier layers are AlGaInP; one well layer and barrier layer is one period, the number of periods is 10, and the thickness of the active layer is 0.15μm; the P-type barrier layer is (Al a Ga 1-a ) 0.5 In 0.5 P layer, thickness is 1000A, a=0.3; P-type limiting layer is AIP layer, thickness is 3000A.

[0057] Embodiment 3:

[0058] An epitaxial structure for optimizing ESD, the structure of which is as described in Example 1, except that the Mg doping concentration of the low-temperature and low-speed layer is 2E+18atom / cm3; the Mg doping concentration of the high-temperature and high-speed layer is 5E+18atom / cm3. The Mg doping concentration of the high-temperature and high-speed layer increases linearly.

[0059] The buffer layer is a GaAs layer with a thickness of 0.8μm; the DBR layer is a periodic structure of alternating AlAs layers and AlGaAs layers, each AlAs layer is 550A thick and the AlGaAs layer is 500A thick; the AlAs layer and the AlGaAs layer are alternately arranged 14 times, with a total of 28 layers; the N-type limiting layer is an AIP layer with a thickness of 3000A; the N-type barrier layer is (Al a Ga 1-a ) 0.5 In 0.5 P layer, thickness is 1000A, a=0.4; the active layer is a periodic structure of well layers and barrier layers arranged alternately, the well layers are GaInP, and the barrier layers are AlGaInP; one well layer and barrier layer is one period, the number of periods is 20, and the thickness of the active layer is 0.2μm; the P-type barrier layer is (Al a Ga 1-a ) 0.5 In 0.5 P layer, thickness is 1000A, a=0.4; P-type limiting layer is AIP layer, thickness is 3000A.

[0060] Embodiment 4:

[0061] A method for growing an epitaxial structure for preparing the optimized ESD described in Example 1 comprises the following steps:

[0062] S1: placing the substrate into a reaction chamber of a metal organic chemical vapor deposition device, and purging the reaction chamber with hydrogen.

[0063] The reaction chamber pressure was set to 55 mbar and the temperature was set to 750° C. for 10 minutes.

[0064] The reaction chamber pressure was maintained at 55 mbar and the temperature was maintained at 750° C. At the same time, 120 sccm of TMGa was introduced into the reaction chamber for 6 minutes to grow a buffer layer with a thickness of 0.5 um on the substrate.

[0065] The reaction chamber pressure was set to 55 mbar and the temperature to 750°C. At the same time, 400 sccm of AsH3 and 600 sccm of TMAl were introduced into the reaction chamber to grow an AlAs layer. Then 600 sccm of TMAl and 150 sccm of TMGa were introduced to grow an AlGaAs layer. The growth was alternating for about 30 minutes to form a 28-layer periodic DBR on the buffer layer. At the same time, about 30 sccm of Si2H6 was introduced, and the doping concentration of Si was 2E+18atom / cm3.

[0066] The AsH3 channel was closed, and 1000sccm of PH3, 400sccm of TMIn and 150sccm of TMAl were introduced into the reaction chamber at the same time. The doping concentration of Si was 1E+18atom / cm3, and the reaction lasted for 10 minutes to form an N-type confinement layer.

[0067] The specific process of N-type barrier layer growth is as follows:

[0068] Maintaining the PH3 atmosphere, the designed 400 sccmTMIn and 150TMAl and 35 sccmTMGa flow rates were introduced for 2 minutes to form an N-type barrier layer on the N-type restriction layer.

[0069] S2: Alternately grow well layers and barrier layers of a multi-quantum well active layer on the N-type barrier layer, wherein the thickness of the multi-quantum well active layer is 0.2 μm; the well layer is GaInP, and the barrier layer is AlGaInP, each growth of the well layer and the barrier layer is a cycle, and the number of GaInP / AlGaInP cycles is 15; when growing the well layer, set the reaction chamber temperature to 750 degrees for 20 minutes to form a multi-quantum well active layer on the barrier DBR group.

[0070] S3: Set the reaction chamber pressure to 55 mbar, the temperature to 750°C, maintain PH3, turn off AsH3, and introduce the designed 300 sccm TMIn, 165 sccm TMAl, and 35 sccm TMGa flow rates for 2 minutes to grow a P-type barrier layer in the multi-quantum well active region layer.

[0071] The reaction chamber pressure was set to 55 mbar and the temperature to 750°C. 800 sccm of PH3, 300 sccm of TMIn and 165 sccm of TMAl were introduced into the reaction chamber. The Mg doping concentration was 1.5E+18 atom / cm3. The reaction was continued for 5 minutes to form a P-type confinement layer on the electron blocking layer.

[0072] S4: Set the reaction chamber pressure to 55 mbar and the temperature to 750°C, introduce 300 sccm of PH3 and 75 sccm of TMGa into the reaction chamber, and design the growth rate to be 6 A / s; the Mg doping concentration is 1E+18 atom / cm3, and continue for 30 minutes to form a 1 um low-temperature and low-speed layer on the electron blocking layer.

[0073] The reaction chamber pressure was set to 55 mbar. In the subsequent 30 minutes of growth time, the temperature was uniformly increased from 750°C to 850°C, PH3 was gradually increased from 300 sccm to 800 sccm, and the TMGa flow rate was linearly increased from 75 sccm to 375 sccm. The designed growth rate was 30 A / s, and the Mg doping concentration was 5E+18 atom / cm3, forming a 3 um uniformly variable high-temperature and high-speed layer.

[0074] Embodiment 5:

[0075] A method for growing an epitaxial structure to optimize ESD, the steps are as described in Example 4, except that in step S1, the buffer layer growth process is specifically as follows:

[0076] The reaction chamber pressure was set to 50 mbar and the temperature to 700° C. At the same time, 100 sccm of TMGa was introduced into the reaction chamber for 4 minutes to grow a buffer layer.

[0077] The specific process of DBR layer growth is as follows:

[0078] The reaction chamber pressure was set to 50 mbar and the temperature to 700°C. At the same time, 300 sccm of AsH3 and 400 sccm of TMAl were introduced into the reaction chamber to grow an AlAs layer. Then 400 sccm of TMAl and 100 sccm of TMGa were introduced to grow an AlGaAs layer. The growth was alternating for 30 minutes to form a DBR layer on the buffer layer.

[0079] The specific growth process of the N-type confinement layer is as follows:

[0080] The AsH3 channel was closed, and 800sccm of PH3, 300sccm of TMIn and 150sccm of TMAl were introduced into the reaction chamber at the same time. The doping concentration of Si was 1E+18atom / cm 3 , and continued for 5 minutes to form an N-type restriction layer.

[0081] The specific process of N-type barrier layer growth is as follows:

[0082] The PH3 atmosphere is maintained, and the designed flow rates of 300 sccmTMIn, 150TMAl, and 30 sccmTMGa are introduced for 2 minutes to form an N-type barrier layer on the N-type restriction layer.

[0083] In step S2, the active layer growth process is specifically as follows:

[0084] Maintaining the PH3 atmosphere for 10 minutes, alternately growing the well layer and the barrier layer of the multi-quantum well active layer; the well layer is GaInP, and the barrier layer is AlGaInP; each growth of the well layer and the barrier layer is a cycle, and the number of GaInP / AlGaInP cycles is 10; forming an active layer.

[0085] In step S3, the P-type barrier layer growth process is specifically as follows:

[0086] After the growth of the active layer is completed, the temperature of the reaction chamber is set to 700° C., the pH is maintained at 3, and the designed flow rates of 300 sccmTMIn, 150 sccmTMAl, and 30 sccmTMGa are introduced for 2 minutes to form an N-type barrier layer.

[0087] The specific growth process of the P-type confinement layer is as follows:

[0088] The reaction chamber temperature was set at 700°C and the pressure was set at 50 mbar. 800 sccm of PH3, 300 sccm of TMIn and 150 sccm of TMAl were introduced into the reaction chamber. The doping concentration of Mg was 1E+18 atom / cm3. The reaction was continued for 5 minutes to form a P-type confinement layer.

[0089] In step S4, the growth process of the P-type current spreading layer is specifically as follows:

[0090] The reaction chamber temperature was set at 700°C and the pressure was set at 50 mbar. 200 sccm of PH3 and 50 sccm of TMGa were introduced into the reaction chamber. The Mg doping concentration was 0.5E+18 atom / cm3 and the reaction lasted for 20 minutes to form a low-temperature and low-speed layer.

[0091] The reaction chamber temperature was set at 800°C and the pressure was set at 50 mbar. 400 sccm of PH3 and 300 sccm of TMGa were introduced into the reaction chamber. The doping concentration of Mg was 2E+18 atom / cm3 for 20 minutes to form a gradient high-temperature and high-speed layer.

[0092] Embodiment 6:

[0093] A method for growing an epitaxial structure to optimize ESD, the steps are as described in Example 4, except that in step S1, the buffer layer growth process is specifically as follows:

[0094] The reaction chamber pressure was set to 60 mbar and the temperature to 800° C. At the same time, 120 sccm of TMGa was introduced into the reaction chamber for 6 minutes to grow a buffer layer.

[0095] The specific process of DBR layer growth is as follows:

[0096] The reaction chamber pressure was set to 60 mbar and the temperature to 800°C. At the same time, 500 sccm of AsH3 and 800 sccm of TMAl were introduced into the reaction chamber to grow an AlAs layer. Then, 800 sccm of TMAl and 200 sccm of TMGa were introduced to grow an AlGaAs layer. The growth was repeated alternately for 60 minutes to form a DBR layer on the buffer layer.

[0097] The specific growth process of the N-type confinement layer is as follows:

[0098] The AsH3 channel was closed, and 1200 sccm of PH3, 500 sccm of TMIn and 200 sccm of TMAl were introduced into the reaction chamber at the same time. The doping concentration of Si was 3E+18 atom / cm 3 , and continued for 15 minutes to form an N-type confinement layer.

[0099] The specific process of N-type barrier layer growth is as follows:

[0100] The PH3 atmosphere is maintained, and the designed flow rates of 500 sccmTMIn, 200TMAl, and 40 sccmTMGa are introduced for 5 minutes to form an N-type barrier layer on the N-type restriction layer.

[0101] In step S2, the active layer growth process is specifically as follows:

[0102] Maintaining the PH3 atmosphere for 20 minutes, alternately growing the well layer and the barrier layer of the multi-quantum well active layer; the well layer is GaInP, and the barrier layer is AlGaInP; each growth of the well layer and the barrier layer is a cycle, and the number of GaInP / AlGaInP cycles is 20; forming an active layer.

[0103] In step S3, the P-type barrier layer growth process is specifically as follows:

[0104] After the active layer growth is completed, the temperature of the reaction chamber is set to 800° C., the pH is maintained at 3, and the designed flow rates of 500 sccmTMIn, 200 sccmTMAl, and 40 sccmTMGa are introduced for 5 minutes to form an N-type barrier layer.

[0105] The specific growth process of the P-type confinement layer is as follows:

[0106] The reaction chamber temperature was set at 800°C and the pressure was set at 60 mbar. 1200 sccm of PH3, 500 sccm of TMIn and 200 sccm of TMAl were introduced into the reaction chamber. The Mg doping concentration was 3E+18 atom / cm3. The reaction was continued for 15 minutes to form a P-type confinement layer.

[0107] In step S4, the growth process of the P-type current spreading layer is specifically as follows:

[0108] The reaction chamber temperature was set at 800°C and the pressure was set at 60 mbar. 400 sccm of PH3 and 100 sccm of TMGa were introduced into the reaction chamber. The Mg doping concentration was 2E+18 atom / cm3 and the reaction lasted for 30 minutes to form a low-temperature and low-speed layer.

[0109] The reaction chamber temperature was set at 1000°C and the pressure was set at 60 mbar. 800 sccm of PH3 and 500 sccm of TMGa were introduced into the reaction chamber. The doping concentration of Mg was 5E+18 atom / cm3 for 30 minutes to form a gradient high-temperature and high-speed layer.

[0110] Comparative Example

[0111] In Table 1, each wafer number represents an epitaxial layer structure, and a whole wafer is taken as a test sample for each epitaxial layer structure. Five wafers are taken from the implementation group and the two control groups for comparison tests on the lop mean and voltage level.

[0112] The following is a comparative example and combined with the attached Figure 3 The present invention is further described, but is not limited thereto.

[0113] In Table 1, the different growth schemes of the current spreading layer of the control groups A and B are different from those of Example 4 in that:

[0114] In control group 1, the temperature, TMGa flow rate, and PH3 dosage in the high-temperature and high-speed layer were uniformly grown in the first 1.5um, and the growth was maintained in the last 1.5um;

[0115] In the control group 2, the temperature, TMGa flow rate, and PH3 dosage in the high-temperature and high-speed layer were processed using a transient process instead of a uniformly variable growth process.

[0116] Experimental verification conclusion

[0117] Table 1 shows the yield or pass rate of the chip tested with 2KV ESD. For example, the pass rate of the LED chip No. 1 in the implementation group of Example 4 is 98.23%. It can be seen from Table 1 that the method provided by the present invention is used, and the average value of the positive polarity of the LED in the ESD test reaches 97.89%, while the two comparison groups are 82.62% and 62.31% respectively. The growth method of the gap provided by the present invention significantly improves the pass rate of the ESD test.

[0118] Table 1 is a test comparison table of the embodiments of the present invention

[0119]

[0120] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention specification, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

[0121] In addition, it is understood that although the present invention has been disclosed as a preferred embodiment, the above embodiment is not intended to limit the present invention. For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. An epitaxial structure for optimizing ESD, characterized in that: The invention comprises a substrate, on which a buffer layer, a DBR layer, an N-type limiting layer, an N-type blocking layer, an active layer, a P-type blocking layer, a P-type limiting layer and a P-type current spreading layer are sequentially arranged from bottom to top; The P-type current extension layer is a Gap layer, which includes a low-temperature and low-speed layer and a high-temperature and high-speed layer from bottom to top. The Mg doping concentration in the low-temperature and low-speed layer is consistent, and the Mg doping concentration in the high-temperature and high-speed layer gradually increases. The Mg doping starting concentration of the high-temperature and high-speed layer is consistent with the Mg doping concentration in the low-temperature and low-speed layer.

2. The epitaxial structure for optimizing ESD according to claim 1, characterized in that: The Mg doping concentration of the low-temperature and low-speed layer is 0.5-2E+18atom / cm3; the Mg doping concentration of the high-temperature and high-speed layer is 2-5E+18atom / cm3.

3. The epitaxial structure for optimizing ESD according to claim 1, characterized in that: The gradient form of the Mg doping concentration of the high-temperature and high-speed layer is a linear increase.

4. The epitaxial structure for optimizing ESD according to claim 1, characterized in that: The epitaxial structure of optimizing ESD includes one of the following solutions (1)-(7): (1) The buffer layer is a GaAs layer with a thickness of 0.5-0.8 μm; (2) The DBR layer is a periodic structure in which AlAs layers and AlGaAs layers are arranged alternately. The thickness of each AlAs layer is 550A and the thickness of the AlGaAs layer is 500A. The AlAs layers and AlGaAs layers are arranged alternately 14 times, with a total of 28 layers. (3) The N-type limiting layer is an AIP layer with a thickness of 3000A; (4) N-type barrier layer is (Al a Ga 1-a ) 0.5 In 0.5 P layer, thickness is 1000A, 0.3≤a≤0.4; (5) The active layer is a periodic structure in which well layers and barrier layers are alternately arranged, the well layers are GaInP, and the barrier layers are AlGaInP; one well layer and barrier layer constitute one period, the number of periods is 10-20, and the thickness of the active layer is 0.15 μm-0.2 μm; (6) The P-type barrier layer is (Al a Ga 1-a ) 0.5 In 0.5 P layer, thickness is 1000A, 0.3≤a≤0.4; (7) The P-type limiting layer is an AIP layer with a thickness of 3000A.

5. The epitaxial structure for optimizing ESD according to claim 1, characterized in that: The thickness of the P-type current spreading layer is 4um, of which the first 1um is a low-temperature and low-speed layer; the last 3um is a gradient high-temperature and high-speed layer.

6. A method for preparing an epitaxial structure for optimizing ESD, characterized in that: Here are the steps: S1: placing the substrate into a reaction chamber of a metal organic chemical vapor deposition device, and sequentially growing a buffer layer, a DBR layer, an N-type restriction layer and an N-type barrier layer on the substrate; S2: growing an active layer on the N-type barrier layer; S3: growing a P-type barrier layer and a P-type confinement layer on the active layer; S4: growing a P-type current spreading layer on the P-type limiting layer, and growing a low-temperature and low-speed layer and a high-temperature and high-speed layer through process control.

7. The method for preparing an epitaxial structure for optimizing ESD according to claim 6, characterized in that: In step S1, the buffer layer growth process is specifically as follows: Set the reaction chamber pressure to 50-60 mbar and the temperature to 700-800°C, and introduce 100-120 sccm of TMGa into the reaction chamber for 4-6 minutes to grow a buffer layer; The specific process of DBR layer growth is as follows: The reaction chamber pressure is set to 50-60 mbar and the temperature is set to 700-800° C. At the same time, 300-500 sccm of AsH3 and 400-800 sccm of TMAl are introduced into the reaction chamber to grow an AlAs layer, and then 400-800 sccm of TMAl and 100-200 sccm of TMGa are introduced to grow an AlGaAs layer. The growth is alternating for 30-60 minutes to form a DBR layer on the buffer layer. The specific growth process of the N-type confinement layer is as follows: Close the AsH3 channel, and introduce 800-1200sccm of PH3, 300-500sccm of TMIn and 150-200sccm of TMAl into the reaction chamber. The doping concentration of Si is 1-3E+18atom / cm 3 , lasting 5-15 minutes, forming an N-type restriction layer; The specific process of N-type barrier layer growth is as follows: Maintaining the PH3 atmosphere, the designed flow rates of 300-500 sccmTMIn, 150-200 TMAl, and 30-40 sccmTMGa are introduced for 2-5 minutes to form an N-type barrier layer on the N-type restriction layer.

8. The method for preparing an epitaxial structure for optimizing ESD according to claim 6, characterized in that: In step S2, the active layer growth process is specifically as follows: Maintaining the PH3 atmosphere for 10-20 minutes, alternately growing the well layer and the barrier layer of the multi-quantum well active layer; the well layer is GaInP, and the barrier layer is AlGaInP; each growth of the well layer and the barrier layer is a cycle, and the number of GaInP / AlGaInP cycles is 10 to 20; forming an active layer.

9. The method for preparing an epitaxial structure for optimizing ESD according to claim 6, characterized in that: In step S3, the P-type barrier layer growth process is specifically as follows: After the active layer is grown, the temperature of the reaction chamber is set to 700-800°C, the pH is maintained at 3, and the designed flow rates of 300-500 sccmTMIn, 150-200 sccmTMAl, and 30-40 sccmTMGa are introduced for 2-5 minutes to form an N-type barrier layer; The specific growth process of the P-type confinement layer is as follows: Set the reaction chamber temperature to 700-800°C and the pressure to 50-60mbar, introduce 800-1200sccm of PH3, 300-500sccm of TMIn and 150-200sccm of TMAl into the reaction chamber, and the Mg doping concentration to 1-3E+18atom / cm3 for 5-15 minutes to form a P-type confinement layer.

10. The method for preparing an epitaxial structure for optimizing ESD according to claim 6, characterized in that: In step S4, the growth process of the P-type current spreading layer is specifically as follows: Set the reaction chamber temperature to 700-800°C and the pressure to 50-60mbar, introduce 200-400sccm of PH3 and 50-100sccm of TMGa into the reaction chamber; the Mg doping concentration is 0.5-2E+18atom / cm3, and continue for 20-30 minutes to form a low-temperature and low-speed layer; The reaction chamber temperature is set at 800-1000°C and the pressure is set at 50-60mbar. 400-800sccm of PH3 and 300-500sccm of TMGa are introduced into the reaction chamber. The doping concentration of Mg is 2-5E+18atom / cm3 for 20-30 minutes to form a gradual high-temperature and high-speed layer.

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