A method for reducing driving voltage of LED chip by growing GaN-based epitaxial layer

Abstract

The application relates to the technical field of LED chip, in particular to a GaN-based epitaxial layer growth method for reducing the driving voltage of an LED chip. The growth method comprises the following steps: firstly, growing an N-type GaN layer on a substrate; secondly, introducing 50000-75000 sccm of NH3, 5000-20000 sccm of H2, 50000-80000 sccm of N2, 200-300 sccm of SiH4 and 1000-2000 sccm of TEGa to grow a stress release layer on the N-type GaN layer; thirdly, growing a multi-quantum well active region layer on the stress release layer; fourthly, introducing 45000-60000 sccm of NH3, 1000-2000 sccm of TEGa and 2000-4000 sccm of CP2Mg to grow a low-temperature P-type GaN layer on the multi-quantum well active region layer; and finally, growing a subsequent P layer to obtain a GaN-based epitaxial layer. In the growth method, TEGa is used to replace TMGa, and at the same time, silane and CP2Mg are incorporated, and the high pressure and the five-three ratio are optimized, so that the carbon content can be reduced while the hole injection efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of LED chip, and particularly relates to a GaN-based epitaxial layer growth method for reducing the driving voltage of an LED chip. BACKGROUND

[0002] GaN-based light-emitting diodes (LEDs) are a new type of high-efficiency, environmentally friendly, green solid-state lighting light source, which has the advantages of small size, low power consumption, light weight, low voltage, long service life, high reliability, etc., and is being rapidly applied in urban landscape lighting, traffic signal lights, tunnel lights, mobile phone backlights, outdoor full-color display screens, car interior and exterior lights, etc. The improvement of various performances of LEDs is focused by the industry.

[0003] In the preparation of GaN-based LED epitaxial layers, the characteristics of the stress release layer and the low-temperature P layer are important factors affecting the electrical properties of the LED. Since the MO source molecule contains carbon, whether the thermal decomposition process will cause the incorporation of carbon impurities into the epitaxial layer has always been a technical problem of concern. In the current technical solution for growing LED epitaxial layers in the reaction chamber of domestic MOCVD, trimethyl gallium is mainly used as the Ga source for reaction growth, which will result in a higher C content in the SRL and LTP layers, affecting the crystalline quality of GaN, and thus affecting the Si doping of the SRL layer and the hole doping of the LTP layer, leading to a higher driving voltage.

[0004] Chinese invention patent with publication number CN114824012A discloses a GaN-based LED epitaxial structure, a preparation method thereof and a light-emitting diode, wherein the low-temperature pGaN layer is formed by alternating growth of a trimethyl gallium layer (TMGa) with a high carbon impurity content and a triethyl gallium layer (TEGa) with a low carbon impurity content, which can reduce the carbon impurity content in the low-temperature PGaN layer. However, since TEGa will affect the hole injection efficiency, the proportion of TEGa cannot be increased to further reduce the carbon impurity content in the LED. SUMMARY

[0005] In order to overcome the defects of the above-mentioned prior art, the technical problem to be solved by the present application is to provide a GaN-based epitaxial layer growth method which can not only reduce the carbon content of the LED and the driving voltage, but also improve the hole injection efficiency and the light efficiency.

[0006] In order to solve the above technical problems, the technical scheme adopted by the present application is as follows: a GaN-based epitaxial layer growth method for reducing the driving voltage of an LED chip, comprising the following steps:

[0007] S1: growing an N-type GaN layer on a substrate;

[0008] S2: introducing 50000-75000sccm of NH3, 5000-20000sccm of H2 and 50000-80000sccm of N2, 200-300sccm of SiH4 and 1000-2000sccm of TEGa, growing a stress release layer on the N-type GaN layer;

[0009] S3: growing a multi-quantum well active region layer on the stress release layer;

[0010] S4: introducing 45000-60000sccm of NH3 and 1000-2000sccm of TEGa and 2000-4000sccm of CP2Mg, growing a low-temperature P-type GaN layer on the multi-quantum well active region layer;

[0011] S5: growing a subsequent P layer to obtain a GaN-based epitaxial layer.

[0012] The GaN-based epitaxial layer growth method provided by the application has the advantages that: the stress release layer and the low-temperature P-type GaN layer are grown by selecting TEGa as a gallium source instead of the existing TMGa, the beta hydride of TEGa has a lower activation energy and is more likely to undergo a beta hydride elimination reaction. The beta hydride elimination reaction is that a hydrogen atom at a beta position in an ethyl group is transferred to Ga, thereby decomposing a molecule containing a metal-hydrogen bond and a stable olefin containing a double bond. The beta hydride elimination reaction of TEGa occurs both in the gas phase and on the surface of GaN, which is conducive to reducing carbon contamination from metal organic compounds and improving the crystalline quality of the grown layer and the doping effect, thereby reducing the driving voltage.

[0013] The application uses TEGa to replace TMGa, and by incorporating silane and CP2Mg and optimizing the pressure and the ratio of the three, the carbon content can be reduced while the hole injection efficiency is improved. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 Fig. 1 is a structural schematic diagram of a GaN-based epitaxial layer according to the embodiment of the application;

[0015] Figure 2 Fig. 2 is a SIMS test diagram of the first embodiment and the second embodiment of the application;

[0016] Label explanation: 1, substrate; 2, buffer layer; 3, U-shaped GaN layer; 4, N-type GaN layer; 5, stress release layer; 6, multi-quantum well active region layer; 7, low-temperature P-type GaN layer; 8, P-type GaN layer; 9, P-type contact layer. DETAILED DESCRIPTION

[0017] In order to explain the technical content of the present application, the purposes and effects achieved, the following will be described in conjunction with the embodiments and the accompanying drawings.

[0018] The most critical idea of the present application is that, by using TEGa to replace TMGa, incorporating silane and CP2Mg, and optimizing the pressure and the ratio of five to three, the carbon content can be reduced while the hole injection efficiency is improved.

[0019] Please refer to Figure 1 The GaN-based epitaxial layer growth method for reducing the driving voltage of the LED chip provided by the present application comprises the following steps:

[0020] S1: growing an N-type GaN layer on a substrate;

[0021] S2: introducing 50000-75000sccm of NH3, 5000-20000sccm of H2, 50000-80000sccm of N2, 200-300sccm of SiH4 and 1000-2000sccm of TEGa, growing a stress release layer on the N-type GaN layer;

[0022] S3: growing a multi-quantum well active region layer on the stress release layer;

[0023] S4: introducing 45000-60000sccm of NH3, 1000-2000sccm of TEGa and 2000-4000sccm of CP2Mg, growing a low-temperature P-type GaN layer on the multi-quantum well active region layer;

[0024] S5: growing a subsequent P layer to obtain a GaN-based epitaxial layer.

[0025] As can be seen from the above description, the GaN-based epitaxial layer growth method provided by the present application has the following beneficial effects: the stress release layer and the low-temperature P-type GaN layer are grown by using TEGa as the gallium source instead of the existing TMGa, the beta hydride of TEGa has a lower activation energy and is more likely to undergo elimination reaction. The beta hydride elimination reaction is that one hydrogen atom in the beta position of the ethyl group is transferred to Ga, thereby decomposing a molecule containing a metal-hydrogen bond and a stable olefin containing a double bond. The beta hydride elimination reaction of TEGa occurs both in the gas phase and on the surface of GaN, which is beneficial to reducing the carbon contamination from the metal organic compound and improving the crystalline quality of the grown layer and the doping effect, thereby reducing the driving voltage.

[0026] TEGa as a monomer adsorbs and decomposes through a β-hydrogen elimination process, producing ethylene, which does not deposit carbon; at low temperature and high incident TMGa flux, there is a reaction pathway involving trapped C2Hx radicals, which deposits carbon, so TEGa is a better source gas than TMGa when low carbon levels in the film are desired.

[0027] The stress release layer and the low-temperature P-type GaN layer use TEGa to replace TMGa, which can completely inhibit radial overgrowth and maintain a low growth temperature during MOCVD (metal organic chemical vapor deposition) growth, not only reducing the driving voltage, but also reducing the growth temperature and difficulty, and preparing GaN-based epitaxial layers under simpler conditions.

[0028] By using TEGa to replace TMGa, incorporating silane and CP2Mg, and optimizing the high pressure and five-to-three ratio, the application can reduce carbon content while improving hole injection efficiency. Silane fills the stress release layer, and CP2Mg provides holes in the P layer.

[0029] The ratio of NH3, TEGa and CP2Mg in S4 affects the growth rate and crystalline quality, and the five-to-three ratio refers to the ratio of NH3 to TMGa (molar ratio of five elements to three elements, N in NH3 is a five-element in the application, and Ga in TMGa is a three-element). Increasing the five-to-three ratio will slow down the growth rate, and the optimal five-to-three ratio will improve the crystalline quality.

[0030] Further, the stress release layer is grown in a reaction chamber with a temperature of 700-900°C and a pressure of 300-500 Torr.

[0031] As described above, the temperature and pressure during the growth of the stress release layer affect the crystalline quality and the silane filling effect.

[0032] Further, the low-temperature P-type GaN layer is grown in a reaction chamber with a temperature of 700-800°C and a pressure of 400-600 Torr.

[0033] As described above, the temperature and pressure during the growth of the low-temperature P-type GaN layer affect the crystalline quality and the Mg doping effect.

[0034] Further, the thickness of the low-temperature P-type GaN layer is 40-80 nm.

[0035] As described above, the thickness within a certain range will improve the antistatic effect, and excessive thickness will reduce the light Droop effect, that is, the possibility of brightness decrease.

[0036] Further, the multi-quantum well active region layer comprises 14-16 groups of In x Ga 1-x N layers and GaN layers.

[0037] Further, the In x Ga 1-x N layer is grown in a reaction chamber, the temperature of the reaction chamber is 800℃, and the pressure is 100-300 Torr.

[0038] Further, the thickness of the In x Ga 1-x N layer is 3-5 nm, and the thickness of the GaN layer is 9-15 nm.

[0039] Further, the P layer comprises a P-type GaN layer and a P-type contact layer which are stacked in sequence, and the P-type GaN layer is stacked with the low-temperature P-type GaN layer.

[0040] Further, the P-type contact layer is grown in a reaction chamber, the temperature of the reaction chamber is 850-1080℃, and the pressure is 100-300 Torr.

[0041] Further, it further comprises S6: heating at a temperature of 650-850℃ for 5-15 min.

[0042] Please refer to Figure 1 , the embodiment one of the present application is:

[0043] A GaN-based epitaxial layer growth method for reducing the driving voltage of an LED chip, comprising the following steps:

[0044] S1: placing a substrate 1 into a reaction chamber of a metal organic chemical vapor deposition device;

[0045] S2: setting the temperature of the reaction chamber to 825℃, the pressure to 100 Torr, and introducing ammonia, nitrogen and 100 sccm of TMGa, and maintaining for 1 min; and growing a 0.1 um buffer layer 2 on the substrate 1;

[0046] S3: setting the temperature of the reaction chamber to 1150℃, the pressure to 150 Torr, and introducing ammonia, nitrogen and TMGa, and maintaining for 12 min, so as to grow a 2 um U-shaped GaN layer 3 on the buffer layer 2;

[0047] S4: setting the temperature of the reaction chamber to 1100℃, the pressure to 500 Torr, and introducing nitrogen, hydrogen, ammonia and TMGa; and growing a 2 um N-type GaN layer 4 on the U-shaped GaN layer 3;

[0048] S5: set the temperature of the reaction chamber to 900 DEG C, the pressure to 300 Torr, input 50000 sccm of NH3, 5000 sccm of H2 and 50000 sccm of N2, input 200 sccm of SiH4 and 1700 sccm of TEGa, grow a 0.2um stress release layer 5 on the N-type GaN layer 4;

[0049] S6: grow a 4nm In x Ga 1-x N(0 < x < 1) layer and a 12nm GaN layer in sequence;

[0050] grow the In x Ga 1-x N(0 < x < 1) layer, set the temperature of the reaction chamber to 800 DEG C and the pressure to 200 Torr;

[0051] grow the GaN layer, set the temperature of the reaction chamber to 900 DEG C and the pressure to 200 Torr;

[0052] S7: repeat S6 for 15 times to form a multi-quantum well active region layer 6;

[0053] S8: set the temperature of the reaction chamber to 770 DEG C and the pressure to 600 Torr, input 55000 sccm of NH3 and 1900 sccm of TEGa, input 3000 sccm of CP2Mg, grow a 60nm low-temperature P-type GaN layer 7 on the multi-quantum well active region layer 6;

[0054] S9: set the temperature of the reaction chamber to 890 DEG C and the pressure to 200 Torr, grow a 200nm P-type GaN layer 8;

[0055] S10: set the temperature of the reaction chamber to 900 DEG C and the pressure to 200 Torr, grow a 150nm P-type contact layer 9;

[0056] S11: set the temperature of the reaction chamber to 700 DEG C and keep for 10min, complete the preparation of the GaN-based epitaxial layer.

[0057] Embodiment two of the present application is:

[0058] A GaN-based epitaxial layer growth method for reducing the driving voltage of an LED chip, comprising the following steps:

[0059] S1: place a substrate 1 into a reaction chamber of a metal organic chemical vapor deposition device;

[0060] S2: set the temperature of the reaction chamber to 825 DEG C and the pressure to 100 Torr, input ammonia, nitrogen and 100 sccm of TMGa, and keep for 2min; grow a 0.2um buffer layer 2 on the substrate 1;

[0061] S3: The temperature of the reaction chamber is set to 1150℃, the pressure is set to 150 Torr, ammonia, nitrogen and TMGa are introduced, and the growth of 3um U-shaped GaN layer 3 on the buffer layer 2 is performed for 11 min;

[0062] S4: The temperature of the reaction chamber is set to 1100℃, the pressure is set to 500 Torr, nitrogen, hydrogen, ammonia and TMGa are introduced, and 2um N-type GaN layer 4 is grown on the U-shaped GaN layer 3;

[0063] S5: The temperature of the reaction chamber is set to 700℃, the pressure is set to 500 Torr, 60000sccm of NH3, 6000sccm of H2 and 60000sccm of N2 are introduced, 300sccm of SiH4 and 2000sccm of TEGa are introduced, and 0.3um stress release layer 5 is grown on the N-type GaN layer 4;

[0064] S6: 3nm In x Ga 1-x N(0<x<1) layer and 9nm GaN layer are sequentially grown;

[0065] When the In x Ga 1-x N(0<x<1) layer is grown, the temperature of the reaction chamber is set to 800℃, and the pressure is set to 100 Torr;

[0066] When the GaN layer is grown, the temperature of the reaction chamber is set to 900℃, and the pressure is set to 200 Torr;

[0067] S7: The S6 is repeated for 14 times to form a multi-quantum well active region layer 6;

[0068] S8: The temperature of the reaction chamber is set to 750℃, the pressure is set to 500 Torr, 60000sccm of NH3 and 2000sccm of TEGa are introduced, 2000sccm of CP2Mg is introduced, and 40nm low-temperature P-type GaN layer 7 is grown on the multi-quantum well active region layer 6;

[0069] S9: The temperature of the reaction chamber is set to 890℃, the pressure is set to 200 Torr, and 200nm P-type GaN layer 8 is grown;

[0070] S10: The temperature of the reaction chamber is set to 850℃, the pressure is set to 100 Torr, and 150nm P-type contact layer 9 is grown;

[0071] S11: The temperature of the reaction chamber is set to 650℃, and the preparation of the GaN-based epitaxial layer is completed for 5 min.

[0072] Embodiment three of the present application is:

[0073] A GaN-based epitaxial layer growth method for reducing the driving voltage of LED chip, comprising the following steps:

[0074] S1: Put the substrate 1 into the reaction cavity of the metal organic chemical vapor deposition device;

[0075] S2: Set the temperature of the reaction cavity to 825℃, the pressure to 100 Torr, and introduce ammonia, nitrogen and 100 sccm of TMGa for 1 min; grow a 0.15 um buffer layer 2 on the substrate 1;

[0076] S3: Set the temperature of the reaction cavity to 1150℃, the pressure to 150 Torr, and introduce ammonia, nitrogen and TMGa for 13 min, so as to grow a 2.5 um U-shaped GaN layer 3 on the buffer layer 2;

[0077] S4: Set the temperature of the reaction cavity to 1100℃, the pressure to 500 Torr, and introduce nitrogen, hydrogen, ammonia and TMGa; grow a 2 um N-type GaN layer 4 on the U-shaped GaN layer 3;

[0078] S5: Set the temperature of the reaction cavity to 700℃, the pressure to 400 Torr, and introduce 75000 sccm of NH3, 20000 sccm of H2 and 80000 sccm of N2, and introduce 250 sccm of SiH4 and 1000 sccm of TEGa, so as to grow a 0.25 um stress release layer 5 on the N-type GaN layer 4;

[0079] S6: Grow a 5 nm In x Ga 1-x N(0<x<1) layer and a 15 nm GaN layer in sequence;

[0080] When growing the In x Ga 1-x N(0<x<1) layer, set the temperature of the reaction cavity to 800℃ and the pressure to 300 Torr;

[0081] When growing the GaN layer, set the temperature of the reaction cavity to 900℃ and the pressure to 200 Torr;

[0082] S7: Repeat S6 for 16 times to form a multi-quantum well active region layer 6;

[0083] S8: Set the temperature of the reaction cavity to 800℃, the pressure to 400 Torr, and introduce 45000 sccm of NH3 and 1000 sccm of TEGa, and introduce 4000 sccm of CP2Mg, so as to grow a 80 nm low-temperature P-type GaN layer 7 on the multi-quantum well active region layer 6;

[0084] S9: set the temperature of the reaction cavity to 890℃, the pressure to 200Torr, and grow a 200nm P-type GaN layer 8;

[0085] S10: set the temperature of the reaction cavity to 1080℃, the pressure to 300Torr, and grow a 150nm P-type contact layer 9;

[0086] S11: set the temperature of the reaction cavity to 850℃, and keep for 15min, to complete the preparation of the GaN-based epitaxial layer.

[0087] The comparative example one of the present application is: (Ga source is TMGa)

[0088] The difference between the comparative example one and the example one is only that:

[0089] S5 is replaced by: set the temperature of the reaction cavity to 900℃, the pressure to 300Torr, input 50000sccm of NH3, 5000sccm of H2 and 50000sccm of N2, input 200sccm of SiH4 and 400sccm of TMGa, and grow a 0.2um stress release layer 5 on the N-type GaN layer 4;

[0090] S8 is replaced by: set the temperature of the reaction cavity to 770℃, the pressure to 600Torr, input 55000sccm of NH3 and 300sccm of TMGa, and grow a 60nm low-temperature P-type GaN layer 7 on the multi-quantum well active region layer 6.

[0091] The comparative example two of the present application is: (low-pressure input TEGa)

[0092] The difference between the comparative example two and the example two is only that: S5 sets the pressure of the reaction cavity to 200Torr, and S8 sets the pressure of the reaction cavity to 300Torr.

[0093] The comparative example three of the present application is: (change the ratio of NH3 to TMGa)

[0094] The difference between the comparative example three and the example two is only that: S5 inputs 3000sccm of NH3, and S8 inputs 3000sccm of NH3.

[0095] The GaN-based epitaxial layers of the example one and the comparative examples one to three are used to prepare LEDs respectively, and photoelectric tests are conducted on the LEDs, and the test results are shown in Table 1 (Table 1 is the average value of a plurality of LED chip parameters).

[0096] Table 1

[0097]

[0098] As shown in Table 1, the LED chip produced by the GaN-based epitaxial layer growth method provided by the present application has a driving voltage reduced by 0.17v, and the amplitude is 5.3%.

[0099] SIMS tests were conducted on the GaN-based epitaxial layers of Example 1 and Comparative Example 1, and the test results are shown in Table 2. Figure 2 (Wherein sample 1 is the epitaxial layer prepared in Example 1, and sample 2 is the epitaxial layer prepared in Comparative Example 1). As shown in Table 2, Figure 2 It can be seen that the carbon content of the epitaxial wafer prepared by the growth method of the present application is lower than that of the epitaxial wafer prepared by using TMGa.

[0100] In summary, in the GaN-based epitaxial layer growth method provided by the present application, TEGa is selected as the gallium source instead of the existing TMGa when growing the stress release layer 5 and the low-temperature P-type GaN layer 7. The β-hydride of TEGa has a lower activation energy and is more likely to undergo elimination reaction. The β-hydride elimination reaction of TEGa is: one hydrogen atom in the β position of the ethyl group is transferred to Ga, thereby decomposing the molecule containing metal-hydrogen bond and stable double bond-containing olefin. The β-hydride elimination reaction of TEGa occurs both in the gas phase and on the surface of GaN, which is beneficial to reduce the carbon contamination from metal organic compounds and improve the crystalline quality of the growth layer and the doping effect, thereby reducing the driving voltage.

[0101] In the present application, TEGa is used to replace TMGa, and by incorporating silane and CP2Mg, as well as optimizing the high pressure and five three ratio, the hole injection efficiency can be improved while reducing the carbon content.

[0102] The above description is only an embodiment of the present application, and does not limit the patent scope of the present application. Any equivalent transformation or direct or indirect application in related technical fields based on the content of the present application specification and drawings is also included in the patent protection scope of the present application.

Claims

1. A GaN-based epitaxial layer growth method for reducing the driving voltage of an LED chip, characterized by, The method comprises the following steps: S1: growing an N-type GaN layer on a substrate; S2: growing a stress release layer on the N-type GaN layer by inputting 50000-75000sccm of NH3, 5000-20000sccm of H2, 50000-80000sccm of N2, 200-300sccm of SiH4 and 1000-2000sccm of TEGa; S3: growing a multi-quantum well active region layer on the stress release layer; S4: growing a low-temperature P-type GaN layer on the multi-quantum well active region layer by inputting 45000-60000sccm of NH3, 1000-2000sccm of TEGa and 2000-4000sccm of CP2Mg; S5: growing a subsequent P layer to obtain a GaN-based epitaxial layer.

2. The GaN-based epitaxial layer growth method according to claim 1, wherein The growth of the stress release layer is performed in a reaction chamber with a temperature of 700-900℃ and a pressure of 300-500Torr.

3. The GaN-based epitaxial layer growth method of claim 1, wherein The growth of the low-temperature P-type GaN layer is performed in a reaction chamber with a temperature of 700-800℃ and a pressure of 400-600Torr.

4. The GaN-based epitaxial layer growth method of claim 1, wherein The thickness of the low-temperature P-type GaN layer is 40-80nm.

5. The GaN-based epitaxial layer growth method of claim 1, wherein The multi-quantum well active region layer includes 14-16 groups of In x Ga 1-x N layers and GaN layers.

6. The GaN-based epitaxial layer growth method of claim 5, wherein Growth of the In x Ga 1-x N layer was performed in a reaction chamber at a temperature of 800 °C and a pressure of 100-300 Torr.

7. The GaN-based epitaxial layer growth method of claim 5, wherein The In x Ga 1-x The thickness of the GaN layer is 9-15 nm.

8. The GaN-based epitaxial layer growth method of claim 1, wherein The P layer comprises a P-type GaN layer and a P-type contact layer which are stacked in sequence, and the P-type GaN layer is stacked with the low-temperature P-type GaN layer.

9. The GaN-based epitaxial layer growth method of claim 8, wherein The growth of the P-type contact layer is performed in a reaction chamber with a temperature of 850-1080℃ and a pressure of 100-300Torr.

10. The GaN-based epitaxial layer growth method of claim 1 wherein, S6: heating at a temperature of 650-850℃ for 5-15min is further included.

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