High efficiency light emitting diode and method of fabricating the same

Abstract

This invention relates to the field of light-emitting diode (LED) technology, specifically to a high-efficiency LED and its fabrication method. The method includes sequentially growing an AlN buffer layer, an undoped GaN layer, an N-type GaN layer, a low-temperature stress relief layer, a multiple quantum well layer, a P-type semiconductor layer, and a P-type ohmic contact layer on a substrate. During the growth of the multiple quantum well layer, quantum well layers and quantum barrier layers are periodically and alternately grown. The quantum well layer is an InGaN layer, and the quantum barrier layer is a combined structure comprising a BInGaN layer-BGaN layer-BN layer-GaN layer. This invention reduces the probability of carriers undergoing non-radiative recombination at defects, thereby improving the luminous efficiency of the LED.

Description

Technical Field

[0001] This invention relates to the field of light-emitting diode technology, and more specifically to high-efficiency light-emitting diodes and their fabrication methods. Background Technology

[0002] Light-emitting diodes (LEDs) have been widely used in indicators, displays, backlighting, projection, and other fields. Compared to other material systems, GaN-based LEDs have significant advantages in both efficiency and reliability.

[0003] GaN-based group III nitride materials, especially GaN materials, are currently the most researched and widely used wide-bandgap compound semiconductor materials. Particularly in the LED field, InGaN ultra-high blue and green LED technology has been commercialized, and InGaN-based LED products are gradually replacing traditional lighting.

[0004] However, GaN materials are generally used in lighting, displays, and other fields to fabricate GaN-based LEDs via MOCVD. The light-emitting region of these LEDs is primarily a multiple quantum well (MQW) structure composed of periodically arranged GaN and InGaN materials, with InGaN as the quantum well material. This is illustrated by the quantum well light-emitting layer structure, growth method, and epitaxial wafer disclosed in publication number CN114242861A. High-quality, high-In-content InGaN / GaN MQW growth is a key issue in realizing long-wavelength light-emitting devices.

[0005] Since InGaN and GaN materials have different optimal growth temperatures, if the GaN quantum barrier layer is grown at a lower temperature, the crystal quality of the quantum well region will deteriorate, reducing the luminescence efficiency.

[0006] Currently, GaN quantum barrier layers are typically grown at relatively high temperatures. However, this causes the InGaN quantum well layer to decompose during the heating process, reducing the In content of the quantum well layer. On the other hand, as the demand for In content within InGaN increases, the temperature of the epitaxial quantum well is much lower than that of the epitaxial quantum barrier, resulting in a larger temperature difference. Therefore, during subsequent epitaxial quantum barrier material production, the already epitaxial quantum well material is prone to decomposition and outward migration due to the higher temperature of the epitaxial quantum barrier, and may even decompose into metallic In, Ga, and other materials. This leads to problems such as a decrease in the crystal quality of the quantum well material, a significant decrease in the quantum efficiency of the corresponding LED, and a larger half-width of the characteristic emission spectrum. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a high-efficiency light-emitting diode and its preparation method.

[0008] The technical solution adopted by the present invention to solve its technical problem is as follows: a method for fabricating high-efficiency light-emitting diodes includes sequentially growing an AlN buffer layer, an undoped GaN layer, an N-type GaN layer, a low-temperature stress relief layer, a multiple quantum well layer, a P-type semiconductor layer, and a P-type ohmic contact layer on a substrate.

[0009] When growing multiple quantum well layers, quantum well layers and quantum barrier layers are grown alternately and periodically. The quantum well layers are InGaN layers, and the quantum barrier layers are a combined structure, which includes BInGaN layer-BGaN layer-BN layer-GaN layer.

[0010] During the growth of the multiple quantum well layer, the growth temperature of the InGaN layer is T0, the growth temperature of the BinGaN sublayer is T1, the growth temperature of the BGaN layer is T2, the growth temperature of the BN layer is T3, and the growth temperature of the GaN layer is T4, where T4 = T3 ≥ T2 ≥ T1 ≥ T0.

[0011] In a single quantum barrier layer, the thickness of the BInGaN layer is W1, the thickness of the BGaN layer is W2, the thickness of the BN layer is W3, and the thickness of the GaN layer is W4, where W4 > W1 ≥ W2 ≥ W3.

[0012] The growth temperature of the InGaN layer is 790℃~810℃, the growth temperature of the BinGaN layer is 810℃~830℃, the growth temperature of the BGaN layer is 830℃~850℃, and the growth temperature of both the BN layer and the GaN layer is 850℃~870℃.

[0013] In a single quantum barrier layer, the thickness of the BInGaN layer is 1nm to 3nm, the thickness of the BGaN layer is 1nm to 2nm, the thickness of the BN layer is 0.5nm to 1nm, and the thickness of the GaN layer is 9nm to 11nm.

[0014] After the quantum well layer growth is complete, the B source is turned on, the In source flow rate gradually changes from the set value for growing the quantum well layer to 0, and the B source flow rate gradually changes from 0 to the B source set value for growing the BGaN layer, thus growing the BinGaN layer.

[0015] After the flow rate stabilizes, a BGaN layer is grown.

[0016] Then, the Ga source is turned off, and a BN layer is grown.

[0017] Then turn on the Ga source and turn off the B source to grow the GaN layer.

[0018] The substrate is one of sapphire substrate, silicon substrate, aluminum nitride substrate, silicon carbide substrate or gallium nitride substrate.

[0019] During the growth of the AlN buffer layer, the growth temperature was controlled at 400℃~650℃, the sputtering power at 2000W~4000W, and the pressure at 1torr~10torr, and finally an AlN buffer layer of 15nm~50nm was deposited.

[0020] Subsequently, in-situ annealing was performed in the MOCVD equipment under a hydrogen atmosphere at a temperature of 1000℃~1200℃, a pressure of 150 torr~500 torr, and a time of 5 min~10 min.

[0021] During the growth of the undoped GaN layer, the growth temperature is controlled at 1050℃~1200℃ and the pressure is controlled at 100 torr~500 torr, and finally an undoped GaN layer of 1μm~3μm is deposited.

[0022] A high-efficiency light-emitting diode (LED) is prepared using the high-efficiency LED preparation method described above.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The quantum barrier layer is a combination structure of BInGaN / BGaN / BN / GaN containing B atoms. The smaller B atoms can easily fill the defect and dislocation positions in InGaN and GaN materials, forming a stable cell structure and reducing the presence of defects. This reduces the probability of carriers undergoing nonradiative recombination and luminescence at the defect sites, thereby improving the luminous efficiency of the light-emitting diode.

[0025] 2. The combined barrier structure of this application changes the traditional square well structure into an edge well structure, which can better confine the charge carriers in the InGaN layer, thereby increasing the radiative recombination probability of electrons and holes and improving the internal quantum efficiency of the epitaxial wafer.

[0026] 3. In the multi-quantum-well layer, the temperature increases from the well layer to the barrier layer, T4=T3≥T2≥T1≥T0, which reduces the direct destructive effect of high temperature on low-temperature quantum wells, thereby reducing the In composition in the InGaN quantum well. Analysis shows that the BinGaN layer acts as an interface depletion layer, and the growth temperature of the BinGaN layer is close to the growth temperature of the InGaN well layer, ensuring that the In composition in the InGaN well layer is not affected, which is beneficial to the improvement of luminous efficiency and also ensures the wavelength uniformity of the epitaxial wafer. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the epitaxial structure of the light-emitting diode prepared according to the present invention;

[0028] Figure 2 This is a schematic diagram of the structure of the multi-quantum well layer of the present invention;

[0029] Figure 3 This is a schematic diagram of the band structure of the blade-shaped well with multiple quantum well layers of the present invention;

[0030] Figure 4 This is the brightness difference between the present invention and the prior art (the quantum barrier layer is a GaN monolayer structure).

[0031] In the figure: 1. Substrate; 2. AlN buffer layer; 3. Undoped GaN layer; 4. N-type GaN layer; 5. Low-temperature stress relief layer; 6. Multiple quantum well layer; 7. P-type semiconductor layer; 8. P-type ohmic contact layer; 61. InGaN layer; 62. BinGaN layer; 63. BGaN layer; 64. BN layer; 65. GaN layer. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1

[0034] Reference Figures 1-4 The high-efficiency light-emitting diode fabrication method involves sequentially growing an AlN buffer layer 2, an undoped GaN layer 3, an N-type GaN layer 4, a low-temperature stress relief layer 5, a multi-quantum well layer 6, a P-type semiconductor layer 7, and a P-type ohmic contact layer 8 on a substrate 1.

[0035] The multi-quantum-well layer 6 includes periodically alternating quantum well layers and quantum barrier layers. The quantum well layer is an InGaN layer 61, and the quantum barrier layer is a combination structure of BInGaN layer 62-BGaN layer 63-BN layer 64-GaN layer 65.

[0036] During the growth of the multiple quantum well layers, the growth temperature of InGaN layer 61 is T0, the growth temperature of BInGaN sublayer 62 is T1, the growth temperature of BGaN layer 63 is T2, the growth temperature of BN layer 64 is T3, and the growth temperature of GaN layer 65 is T4, where T4=T3≥T2≥T1≥T0.

[0037] In a single quantum barrier layer, the thickness of the BInGaN layer 62 is W1, the thickness of the BGaN layer 63 is W2, the thickness of the BN layer 64 is W3, and the thickness of the GaN layer 65 is W4, where W4 > W1 ≥ W2 ≥ W3.

[0038] The growth temperature of the InGaN layer 61 is 790℃~810℃, the growth temperature of the BinGaN layer 62 is 810℃~830℃, the growth temperature of the BGaN layer 63 is 830℃~850℃, and the growth temperatures of the BN layer 64 and the GaN layer 65 are both 850℃~870℃.

[0039] In a single quantum barrier layer, the thickness of the BInGaN layer 62 is 1 nm to 3 nm, the thickness of the BGaN layer 63 is 1 nm to 2 nm, the thickness of the BN layer 64 is 0.5 nm to 1 nm, and the thickness of the GaN layer 65 is 9 nm to 11 nm.

[0040] After the quantum well layer growth is completed, the B source is turned on, the In source flow rate gradually changes from the set value for growing the quantum well layer to 0, and the B source flow rate gradually changes from 0 to the B source set value for growing the BGaN layer 63, and the BinGaN layer 62 is grown.

[0041] After the flow rate stabilizes, a BGaN layer 63 is grown.

[0042] Then, the Ga source was turned off, and a BN layer of 64 was grown.

[0043] Then turn on the Ga source and turn off the B source to grow a GaN layer of 65.

[0044] Example 2

[0045] Based on Example 1, substrate 1 is a substrate on which an epitaxial layer is grown. The substrate 1 is typically one of sapphire (Al2O3) substrate, silicon (Si) substrate, aluminum nitride (AlN) substrate, silicon carbide (6H-SiC) substrate or gallium nitride (GaN) substrate.

[0046] An AlN buffer layer 2 is grown on substrate 1: The AlN buffer layer 2 is deposited using PVD (Physical Vapor Deposition). During the growth of the AlN buffer layer 2, the growth temperature is controlled at 400℃~650℃, the sputtering power is controlled at 2000W~4000W, and the pressure is controlled at 1torr~10torr. Finally, an AlN buffer layer 2 with a diameter of 15nm~50nm is deposited.

[0047] Subsequently, in-situ annealing was performed in an MOCVD (Metal-organic Chemical Vapor Deposition) device under a hydrogen atmosphere at a temperature of 1000℃~1200℃, a pressure of 150 torr~500 torr, and a time of 5 min~10 min.

[0048] An undoped GaN layer 3 is grown on the AlN buffer layer 2: An undoped GaN layer is grown in an MOCVD device. During the growth of the undoped GaN layer, the growth temperature is controlled at 1050℃~1200℃ and the pressure is controlled at 100 torr~500 torr. Finally, an undoped GaN layer 4 of 1μm~3μm is deposited.

[0049] An N-type GaN layer 4 is grown on the undoped GaN layer 3: The N-type GaN layer 4 is grown in an MOCVD apparatus. The N-type GaN layer 4 is an N-type doped GaN layer with Si as the dopant. The doping concentration of this N-type doped GaN layer is 1E19 atoms / cm². 3 ~1E20atoms / cm 3 The temperature in the MOCVD reaction chamber is controlled at 1100℃~1200℃ and the pressure is 100torr~300torr, and finally an N-type doped GaN layer of 1μm~3μm is deposited.

[0050] A low-temperature stress relief layer 5 is grown on the N-type GaN layer 4: the reaction chamber temperature is adjusted to 800-900℃, the reaction chamber pressure is controlled at 100 torr-500 torr, and a stress relief layer with a thickness of 50nm-70nm is grown.

[0051] A multi-quantum well layer 6 is grown on the low-temperature stress relief layer 5. The multi-quantum well layer 6 includes alternating quantum well layers and quantum barrier layers with a stacking period of 3 to 15. The quantum well layer is an InGaN layer 61, and the quantum barrier layer is a combination structure of BInGaN-BGaN-BN-GaN. During the growth of the multi-quantum well layer, the growth temperature of InGaN layer 61 is controlled to be T0, the growth temperature of BInGaN layer 62 is T1, the growth temperature of BGaN layer 63 is T2, the growth temperature of BN layer 64 is T3, and the growth temperature of GaN layer 65 is T4, where T4 = T3 ≥ T2 ≥ T1 ≥ T0.

[0052] Furthermore, the growth temperature of InGaN layer 61 is 790℃~810℃, the growth temperature of BinGaN layer 62 is 810℃~830℃, the growth temperature of BGaN layer 63 is 830℃~850℃, and the growth temperature of BN layer 64 and GaN layer 65 is 850℃~870℃.

[0053] In addition, in a single quantum barrier layer, the thickness of the BInGaN layer 62 is 1nm to 3nm, the thickness of the BGaN layer 63 is 1nm to 2nm, the thickness of the BN layer 64 is 0.5nm to 1nm, and the thickness of the GaN layer 65 is 9nm to 11nm.

[0054] After the quantum well layer growth is complete, turn on the B source, gradually change the In source flow rate from the set value for growing the quantum well layer to 0, and gradually change the B source flow rate from 0 to the B source set value for growing the BGaN layer 63, and grow the BinGaN layer 62; after the flow rate stabilizes, grow the BGaN layer 63; then turn off the Ga source and grow the BN layer 64; then turn on the Ga source and turn off the B source to grow the GaN layer 65.

[0055] When growing the BInGaN layer 62, the B flow rate starts to increase from 0, while the In flow rate starts to decrease from the flow rate when growing the InGaN layer 61. When In becomes 0, the flow rate is determined to be stable when the B flow rate maintains a certain value and no longer increases, based on the mass flow meter detection, and then the BGaN layer 63 is grown.

[0056] A P-type semiconductor layer 7 is grown on the multi-quantum-well layer 6. The P-type semiconductor layer 7 is a composite layer consisting of a sequentially deposited P-type AlGaN electron blocking layer and a P-type GaN layer. The P-type AlGaN electron blocking layer is a Mg-doped AlGaN layer with a Mg doping concentration of 3 × 10⁻⁶. 18 atoms / cm 3 ~8×10 18 atoms / cm 3 The thickness is 50nm–100nm, the growth temperature is 900℃–1000℃, and the growth pressure is 100 torr–200 torr. The p-type GaN layer is a Mg-doped GaN layer with a Mg doping concentration of 3 × 10⁻⁶. 19 atoms / cm 3 ~8×10 19 atoms / cm 3 Thickness 80nm~150nm, growth temperature 900℃~1000℃, growth pressure 300torr~600torr.

[0057] A P-type ohmic contact layer 8 is grown on the P-type semiconductor layer 7: the P-type contact layer is a Mg-doped GaN layer with a Mg doping concentration of 8 × 10⁻⁶. 19 atoms / cm 3 ~3×10 20 atoms / cm 3 Thickness 10nm~30nm, growth temperature 900℃~1000℃, growth pressure 300torr~600torr.

[0058] After the epitaxial structure growth is completed, the temperature of the reaction chamber is lowered and annealed in a nitrogen atmosphere at a temperature of 650℃~850℃ for 5min~15min. The epitaxial growth is then stopped at room temperature, and the preparation is completed.

[0059] Example 3

[0060] This embodiment proposes a high-efficiency light-emitting diode, which consists of a substrate 1, an AlN buffer layer (2), an undoped GaN layer 3, an N-type GaN layer 4, a low-temperature stress relief layer 5, a multi-quantum well layer 6, a P-type semiconductor layer 7, and a P-type ohmic contact layer arranged sequentially. This light-emitting diode is prepared by the preparation method described in Embodiment 1 or Embodiment 2.

[0061] The above description is merely an optional embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for fabricating a high-efficiency light-emitting diode, characterized in that, An AlN buffer layer (2), an undoped GaN layer (3), an N-type GaN layer (4), a low-temperature stress relief layer (5), a multi-quantum well layer (6), a P-type semiconductor layer (7), and a P-type ohmic contact layer (8) are sequentially grown on a substrate (1). During the growth of the multi-quantum well layer (6), the quantum well layer and the quantum barrier layer are grown alternately in a periodic manner. The quantum well layer is an InGaN layer (61), and the quantum barrier layer is a combined structure, which includes a BInGaN layer (62)-BGaN layer (63)-BN layer (64)-GaN layer (65).

2. The method for fabricating a high-efficiency light-emitting diode according to claim 1, characterized in that, During the growth of the multi-quantum-well layer, the growth temperature of the InGaN layer (61) is T0, the growth temperature of the BInGaN sublayer (62) is T1, the growth temperature of the BGaN layer (63) is T2, the growth temperature of the BN layer (64) is T3, and the growth temperature of the GaN layer (65) is T4, where T4 = T3 ≥ T2 ≥ T1 ≥ T0.

3. The method for fabricating a high-efficiency light-emitting diode according to claim 1, characterized in that, In a single quantum barrier layer, the thickness of the BInGaN layer (62) is W1, the thickness of the BGaN layer (63) is W2, the thickness of the BN layer (64) is W3, and the thickness of the GaN layer (65) is W4, where W4 > W1 ≥ W2 ≥ W3.

4. The method for fabricating a high-efficiency light-emitting diode according to claim 1 or 2, characterized in that, The growth temperature of the InGaN layer (61) is 790℃~810℃, the growth temperature of the BinGaN layer (62) is 810℃~830℃, the growth temperature of the BGaN layer (63) is 830℃~850℃, and the growth temperature of the BN layer (64) and the GaN layer (65) is 850℃~870℃.

5. The method for fabricating a high-efficiency light-emitting diode according to claim 1 or 3, characterized in that, In a single quantum barrier layer, the thickness of the BInGaN layer (62) is 1 nm to 3 nm, the thickness of the BGaN layer (63) is 1 nm to 2 nm, the thickness of the BN layer (64) is 0.5 nm to 1 nm, and the thickness of the GaN layer (65) is 9 nm to 11 nm.

6. The method for fabricating a high-efficiency light-emitting diode according to claim 1, characterized in that, After the quantum well layer growth is completed, the B source is turned on, the In source flow rate gradually changes from the set value for growing the quantum well layer to 0, and the B source flow rate gradually changes from 0 to the B source set value for growing the BGaN layer (63), and the BInGaN layer (62) is grown. After the flow rate stabilizes, a BGaN layer is grown (63); Then the Ga source was turned off, and a BN layer (64) was grown; Then turn on the Ga source and turn off the B source to grow a GaN layer (65).

7. The method for fabricating a high-efficiency light-emitting diode according to claim 1, characterized in that, The substrate (1) is one of sapphire substrate, silicon substrate, aluminum nitride substrate, silicon carbide substrate or gallium nitride substrate.

8. The method for fabricating a high-efficiency light-emitting diode according to claim 1, characterized in that, During the growth of the AlN buffer layer (2), the growth temperature was controlled at 400℃~650℃, the sputtering power was 2000W~4000W, and the pressure was 1torr~10torr, and finally an AlN buffer layer of 15nm~50nm was deposited. Subsequently, in-situ annealing was performed in the MOCVD equipment under a hydrogen atmosphere at a temperature of 1000℃~1200℃, a pressure of 150 torr~500 torr, and a time of 5 min~10 min.

9. The method for fabricating a high-efficiency light-emitting diode according to claim 1, characterized in that, During the growth of the undoped GaN layer (3), the growth temperature is controlled at 1050℃~1200℃ and the pressure is 100torr~500torr, and finally an undoped GaN layer of 1μm~3μm is deposited.

10. A high-efficiency light-emitting diode, characterized in that, The light-emitting diode is prepared by the high-efficiency light-emitting diode preparation method described in any one of claims 1-9.

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