Dual-band LED epitaxial wafer and preparation method

Abstract

The application discloses a double-waveband LED epitaxial wafer and a preparation method thereof, and belongs to the technical field of LEDs. The double-waveband LED epitaxial wafer comprises a substrate, wherein a buffer layer, a cutoff layer, a long-waveband N-type semiconductor layer, a long-waveband multi-quantum well layer, a wide-bandgap tunneling PN junction, a short-waveband multi-quantum well layer and a short-waveband P-type semiconductor layer are sequentially arranged on the substrate from bottom to top; the wide-bandgap tunneling PN junction comprises a heavily doped P-type layer and a heavily doped N-type layer from bottom to top, and the proportion of interpenetrating channels in the wide-bandgap tunneling PN junction is 5%-15%. In actual use, the substrate is removed and reversely arranged, so that electrons are firstly injected into the short-waveband multi-quantum well layer to emit light, then the electrons are injected into the long-waveband multi-quantum well layer through the wide-bandgap tunneling PN junction to continue emitting light, and single-chip double-waveband synchronous light emission is realized.

Description

Technical Field

[0001] This invention belongs to the field of LED technology, specifically a dual-band LED epitaxial wafer and its preparation method. Background Technology

[0002] Light-emitting diodes (LEDs), as a new generation of solid-state lighting sources, have been widely used in general lighting, display backlighting, automotive lighting, and signal indication due to their advantages such as high efficiency, energy saving, environmental friendliness, and long lifespan. With increasingly complex application scenarios, single-band LED chips are no longer sufficient to meet the demands, and dual-band or even multi-band integrated LED chips have become a research hotspot.

[0003] In existing technologies, there are several main approaches to achieving dual-band or multi-band light emission:

[0004] Firstly, multi-chip integrated packaging: For example, mixing and packaging independent red LED chips and yellow-green LED chips. Although this method is technically mature, it has problems such as complex packaging process, high cost, large device size, poor heat dissipation performance, and low light field coupling efficiency between different chips.

[0005] Secondly, phosphor conversion technology: This method uses short-wavelength LEDs (such as blue light or ultraviolet light) to excite phosphors to produce long-wavelength light, thereby achieving spectral mixing. However, this method has inherent drawbacks such as low phosphor conversion efficiency, large Stokes energy loss, spectral stability that is greatly affected by temperature, and difficulty in accurately controlling color temperature.

[0006] Third, vertically stacked epitaxial structures: Vertically stacking multiple quantum well light-emitting layers of different wavelengths on the same substrate is an ideal direction for achieving monolithic integration. For example, related technologies have proposed vertical chip structures with a blue quantum well layer as the lower layer and a green quantum well layer as the upper layer. However, this approach faces significant technical challenges: First, the substrate needs to be removed during use, and the number of vertically stacked quantum well layers cannot be too large, otherwise it will affect the light transmission efficiency. Second, the wavelength difference between different quantum well layers needs to be precisely controlled. If the wavelength difference is too small, the light generated by the lower quantum well layer will not be able to pass through effectively, thus affecting the generation efficiency of the corresponding wavelength light of the upper (e.g., green) quantum well layer. In addition, electrons cannot be effectively injected into the upper green quantum well layer after passing through the lower blue quantum well layer.

[0007] In summary, existing dual-band LED technology suffers from problems such as complex processes, high costs, or limited performance. There is an urgent need for a new epitaxial structure and fabrication method to simplify the process, reduce manufacturing costs, and improve device reliability. Summary of the Invention

[0008] This invention addresses the technical problems of complex and costly existing dual-band LED fabrication processes, which require separate packaging or optical coupling. It provides a dual-band LED epitaxial wafer and its fabrication method, aiming to achieve single-chip dual-band light emission by integrating a short-wavelength epitaxial layer and a long-wavelength epitaxial layer on the same substrate and connecting them through a wide-bandgap tunneling PN junction, thereby reducing manufacturing costs and improving device reliability.

[0009] The present invention adopts the following technical solution:

[0010] A dual-band LED epitaxial wafer includes a substrate, on which a buffer layer, a cutoff layer, a long-wavelength N-type semiconductor layer, a long-wavelength multi-quantum-well layer, a wide-bandgap tunneling PN junction, a short-wavelength multi-quantum-well layer and a short-wavelength P-type semiconductor layer are sequentially disposed from bottom to top.

[0011] The wide-bandgap tunneling PN junction comprises, from bottom to top, a heavily doped P-type layer and a heavily doped N-type layer, and the proportion of interpenetrating channels in a unit area of ​​the wide-bandgap tunneling PN junction is 5-15%.

[0012] In the dual-band LED epitaxial wafer, the wide-bandgap tunneling PN junction further includes a P-type buffer layer located between the heavily doped P-type layer and the long-band multi-quantum-well layer, and an N-type buffer layer located between the heavily doped N-type layer and the short-band multi-quantum-well layer.

[0013] In the dual-band LED epitaxial wafer, the doping concentration of the heavily doped P-type layer is 1×10⁻⁶. 16 / mm 3 -1×10 18 / mm 3 The thickness is 5nm-20nm; the doping concentration of the heavily doped N-type layer is 2×10⁻⁶. 16 / mm 3 -1×10 17 / mm 3 The thickness is 5nm-20nm.

[0014] In the dual-band LED epitaxial wafer, the doping concentration of the P-type buffer layer is 1×10⁻⁶. 15 / mm 3 -1×10 17 / mm 3 The thickness is 3nm-5nm; the doping concentration of the N-type buffer layer is 2×10⁻⁶. 15 / mm 3 -1×10 16 / mm 3 The thickness is 3nm-5nm.

[0015] In the dual-band LED epitaxial wafer, the difference between the peak wavelength of the long-wavelength multi-quantum-well layer and the peak wavelength of the short-wavelength multi-quantum-well layer is greater than 50 nm.

[0016] In the dual-band LED epitaxial wafer, the substrate is a GaAs substrate, the long-wavelength multi-quantum-well layer is an InGaAs quantum well layer, and the short-wavelength multi-quantum-well layer is a GaInP quantum well layer.

[0017] In the dual-band LED epitaxial wafer, the heavily doped P-type layer and the P-type buffer layer are Al doped, and the Al content of the P-type buffer layer is lower than that of the heavily doped P-type layer; the heavily doped N-type layer and the N-type buffer layer are Si doped, and the Si doping ratio of the N-type buffer layer is lower than that of the heavily doped N-type layer.

[0018] In the dual-band LED epitaxial wafer, the substrate is a sapphire substrate, and both the long-wavelength multi-quantum-well layer and the short-wavelength multi-quantum-well layer are InGaN / GaN multi-quantum-well structures.

[0019] The method for fabricating the dual-band LED epitaxial wafer includes the following steps:

[0020] S1: Place the substrate in the MOCVD reaction chamber;

[0021] S2: A buffer layer and a cutoff layer are grown sequentially on the substrate;

[0022] S3: Grow a long-wavelength N-type semiconductor layer on the cutoff layer;

[0023] S4: Growing a long-wavelength multi-quantum-well layer on a long-wavelength N-type semiconductor layer;

[0024] S5: Wide-bandgap tunneling PN junctions are grown on long-wavelength multi-quantum-well layers, wherein the proportion of interpenetrating channels in a unit area of ​​wide-bandgap tunneling PN junction 150 is 5-15%;

[0025] S6: Growing short-wavelength multi-quantum-well layers on a wide-bandgap tunneling PN junction;

[0026] S7: Growing a short-wavelength P-type semiconductor layer on a short-wavelength multi-quantum-well layer.

[0027] In the method for preparing a dual-band LED epitaxial wafer, the growth of the wide-bandgap tunneling PN junction in step S5 includes: sequentially growing a P-type buffer layer, a heavily doped P-type layer, a heavily doped N-type layer, and an N-type buffer layer.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. This invention integrates a long-wavelength multi-quantum-well layer, a wide-bandgap tunneling PN junction, and a short-wavelength multi-quantum-well layer sequentially from bottom to top on the same substrate. In practical use, the substrate is removed and the layers are reversed (i.e., the short-wavelength multi-quantum-well layer is below, and the long-wavelength multi-quantum-well layer is above). Electrons are first injected into the short-wavelength multi-quantum-well layer to emit light (high-energy photon emission), and then tunneled through the wide-bandgap tunneling PN junction into the long-wavelength multi-quantum-well layer to continue emitting light (low-energy photon emission). This allows excess energy to relax rapidly in the form of phonons, eliminating the need to overcome additional potential barriers and resulting in higher tunneling efficiency.

[0030] It overcomes the problems of low optical field coupling efficiency and large size of multi-chip packaging, and also avoids Stokes energy loss and spectral thermal drift during phosphor conversion.

[0031] 2. The wide-bandgap tunneling PN junction of the present invention is composed of a heavily doped P-type layer and a heavily doped N-type layer, and the interpenetration channel ratio is limited to 5%-15%. In reverse usage mode (short wavelength below, long wavelength above), the tunneling junction plays a key role in injecting electrons from the short wavelength band into the long wavelength band. The lower limit (5%) ensures sufficient tunneling paths, enabling electrons to efficiently penetrate the reverse barrier and inject into the long wavelength multi-quantum well layer to emit light; the upper limit (15%) prevents excessive interpenetration from increasing leakage current, while avoiding additional absorption of light (high-energy photons) emitted from the lower short wavelength band by the heavily doped region, ensuring that short-wavelength light can be effectively emitted; the wide-bandgap material itself has high transmittance for both short-wavelength and long-wavelength photons, further improving the dual-band light extraction efficiency.

[0032] 3. This invention controls the wavelength difference to >50nm, ensuring sufficient separation of the emission peaks in the short-wavelength and long-wavelength bands, which facilitates independent control of different wavelength bands in subsequent applications; at the same time, the photon energy of the short-wavelength band is higher than that of the long-wavelength band, and in the reverse usage mode, the short-wavelength light will not be significantly absorbed when passing through the long-wavelength layer, thus ensuring the balance of the dual-band output light intensity.

[0033] 4. The setting of the P-type buffer layer and N-type buffer layer in this invention is particularly critical in the reverse usage mode (short wavelength at the bottom, i.e., the N-type buffer layer is closer to the short wavelength light emission region): (1) The N-type buffer layer protects the short wavelength multi-quantum well layer: In the reverse structure, the N-type buffer layer is directly located between the heavily doped N-type layer and the short wavelength multi-quantum well layer. Its low doping concentration and thinness effectively block the diffusion of Si atoms in the heavily doped layer to the short wavelength light emission region, thus protecting the interface quality of the short wavelength quantum well; (2) The P-type buffer layer protects the long wavelength multi-quantum well layer: Similarly, the P-type buffer layer blocks the diffusion of Al atoms to the long wavelength light emission region; (3) Al / Si asymmetric doping design: Al (high diffusion coefficient) drives the formation of interpenetrating channels, and Si (low diffusion coefficient) controls the interpenetration depth. The two work together to precisely lock the ratio of interpenetrating channels in the optimal window of 5%-15%.

[0034] 5. The fabrication method provided by this invention allows for the continuous growth of all epitaxial layers in a single MOCVD or MBE device, making it highly compatible with standard LED epitaxial processes. It eliminates the need for special photolithography or etching steps, significantly reducing manufacturing costs and process complexity. The sequential growth of the P-type buffer layer, heavily doped P-type layer, heavily doped N-type layer, and N-type buffer layer in step S5 ensures a smooth band transition between the tunnel junction and the upper and lower multi-quantum well layers, providing a process guarantee for precise control of the interpenetrating channel ratio. Attached Figure Description

[0035] Figure 1 This is a structural diagram of the dual-band LED epitaxial wafer of this application.

[0036] Figure 2 This is a structural diagram of the wide-bandgap tunneling PN junction of this application.

[0037] Figure 3 This is a schematic diagram of the interpenetrating channel structure of this application.

[0038] In the figure: 100, substrate; 110, buffer layer; 120, cutoff layer; 130, long-wavelength N-type semiconductor layer; 140, short-wavelength N-type semiconductor layer; 150, wide-bandgap tunneling PN junction; 151, growth of P-type buffer layer; 152, heavily doped P-type layer; 153, heavily doped N-type layer; 154, N-type buffer layer; 160, short-wavelength multi-quantum-well layer; 170, short-wavelength P-type semiconductor layer. Detailed Implementation

[0039] In the following embodiments, the growth of each epitaxial layer was performed using a metal-organic chemical vapor deposition (MOCVD) system at a growth temperature of 600℃-800℃ and a growth pressure of 50mbar-500mbar. The source materials used were: trimethylgallium (TMGa) or triethylgallium (TEGa) as the Ga source; trimethylindium (TMIn) as the In source; trimethylaluminum (TMAl) as the Al source; ammonia (NH3) as the N source; phosphine (PH3) as the P source; arsine (AsH3) as the As source; silane (SiH4) as the N-type dopant; and diethylzinc (DEZn) or carbon tetrabromide (CBr4) as the P-type dopant. It should be understood that the following embodiments are only used to more clearly illustrate the present invention and should not be construed as limiting the scope of protection of the present invention.

[0040] Example 1

[0041] This embodiment provides a dual-band LED epitaxial wafer with GaAs as the substrate, an InGaAs quantum well layer (near-infrared band) for the long band, and a GaInP quantum well layer (red band) for the short band.

[0042] like Figure 1 As shown, the dual-band LED epitaxial wafer of this embodiment includes a substrate 100, on which the following are arranged sequentially from bottom to top:

[0043] Buffer layer 110 is used to smooth the substrate surface and provide a high-quality template layer for subsequent epitaxial growth;

[0044] The cutoff layer 120 is used to prevent impurities in the substrate from diffusing upwards into the light-emitting region;

[0045] Long-wavelength N-type semiconductor layer 130, with a thickness of 500nm-1500nm and a doping concentration of 1×10⁻⁶. 17 / mm 3 -5×10 17 / mm 3 ;

[0046] The long-wavelength multi-quantum-well layer 140 is an InGaAs / GaAs multi-quantum-well structure with 3-8 quantum well periods, a well layer thickness of 6nm-10nm, a barrier layer thickness of 10nm-20nm, and a peak wavelength of 900nm-1000nm.

[0047] The wide-bandgap tunneling PN junction 150 includes, from bottom to top, a P-type buffer layer 151, a heavily doped P-type layer 152, a heavily doped N-type layer 153, and an N-type buffer layer 154.

[0048] The short-wavelength multi-quantum-well layer 160 is a GaInP / GaInP multi-quantum-well structure with 3-8 quantum well periods, a well layer thickness of 5nm-8nm, a barrier layer thickness of 8nm-15nm, and a peak wavelength of 620nm-680nm.

[0049] The short-wavelength P-type semiconductor layer 170 has a thickness of 200nm-500nm and a doping concentration of 1×10⁻⁶. 17 / mm 3 -5×10 17 / mm 3 .

[0050] The difference between the peak wavelength of the long-wavelength multi-quantum well layer 140 and the peak wavelength of the short-wavelength multi-quantum well layer 160 is greater than 50 nm. In this embodiment, the difference between their peak wavelengths is approximately 280 nm to 320 nm.

[0051] Parameter control of wide-bandgap tunneling PN junction 150:

[0052] P-type buffer layer 151: Made of AlGaAs material, with a thickness of 3nm-5nm and a doping concentration of 1×10⁻⁶. 15 / mm 3 -1×10 17 / mm 3 The Al content is 10%-20%. The Al content of the P-type buffer layer 151 is lower than that of the heavily doped P-type layer 152.

[0053] Heavily doped p-type layer 152: Made of AlGaAs material, with a thickness of 5nm-20nm and a doping concentration of 1×10⁻⁶. 16 / mm 3 -1×10 18 / mm 3 The Al component accounts for 25%-40%.

[0054] Heavily doped N-type layer 153: Made of AlGaAs material, with a thickness of 5nm-20nm and a doping concentration of 2×10⁻⁶. 16 / mm 3 -1×10 17 / mm³, with an Al component ratio of 25%-40%.

[0055] N-type buffer layer 154: Made of AlGaAs material, with a thickness of 3nm-5nm and a doping concentration of 2×10⁻⁶. 15 / mm 3 -1×10 16 / mm 3 The Al composition ratio is 10%-20%. The Si doping ratio of the N-type buffer layer 154 is lower than that of the heavily doped N-type layer 153.

[0056] In this embodiment, the proportion of interpenetrating channels in the wide-bandgap tunneling PN junction 150 is 5%-15%. This proportion is achieved through coordinated control in the following ways:

[0057] Asymmetric doping concentration design: The heavily doped p-type layer 152 uses a high concentration of Al doping (up to 1×10⁻⁶). 18 / mm 3 Al atoms have a high diffusion coefficient in GaAs materials, forming the "driving source" for interpenetrating channels; the heavily doped N-type layer 153 uses a relatively low concentration of Si doping (maximum 1×10⁻⁶). 17 / mm 3 The diffusion coefficient of Si atoms in GaAs is lower than that of Al, which acts as a "limited acceptor" to control the interpenetration depth. Together, they lock the proportion of interpenetration channels within the optimal window of 5%-15%. The interpenetration channels are channels through which electrons flowing out of the short-wavelength multi-quantum-well layer are injected and enter the long-wavelength multi-quantum-well layer.

[0058] Precise thickness control: The thicknesses of both the heavily doped P-type layer 152 and the heavily doped N-type layer 153 are controlled within the range of 5nm-20nm. This thickness range ensures that the depletion layer width is narrow enough to support the quantum tunneling effect, while avoiding the problems of interpenetration channel runaway exceeding 15% when the thickness is too thin (<5nm) or tunneling probability decrease and operating voltage increase when the thickness is too thick (>20nm).

[0059] Buffer layer protection: The P-type buffer layer 151 uses a low Al content ratio (10%-20%) to act as a "slow release" layer, preventing the heavily doped P-type layer 152 with high Al concentration from directly contacting the long-wavelength multi-quantum-well layer 140 and introducing non-radiative recombination centers. The N-type buffer layer 154 uses a low Si doping ratio to prevent Si atoms in the heavily doped N-type layer 153 from excessively diffusing into the short-wavelength multi-quantum-well layer 160. The thickness of both buffer layers is 3nm-5nm, which can effectively absorb excess dopant atoms without creating significant additional resistance to the tunneling current.

[0060] In practical use, the dual-band LED epitaxial wafer of this embodiment first removes the GaAs substrate 100 by chemical mechanical polishing and selective wet etching, so that the epitaxial layers are reversed, that is, the short-wavelength multi-quantum well layer 160 is on the bottom and the long-wavelength multi-quantum well layer 140 is on the top.

[0061] Under a forward bias voltage, electrons are first injected into the short-wavelength multi-quantum-well layer 160, where they undergo radiative recombination and emit short-wavelength light (red light, 620nm-680nm). Subsequently, the remaining electrons tunnel through the wide-bandgap tunneling PN junction 150 and enter the long-wavelength multi-quantum-well layer 140, where they continue to undergo radiative recombination and emit long-wavelength light (near-infrared light, 900nm-1000nm). Because the injection direction of electrons from the high bandgap (short-wavelength) to the low bandgap (long-wavelength) naturally matches the energy band, the excess energy relaxes rapidly in the form of phonons, significantly improving the tunneling efficiency and thus achieving dual-band synchronous light emission on the same chip.

[0062] The method for fabricating a dual-band LED epitaxial wafer in this embodiment includes the following steps:

[0063] S1: Substrate 100 preparation and high-temperature heat treatment

[0064] A GaAs substrate 100 is provided. The substrate 100 is placed in an MOCVD reaction chamber and heated to 700℃-800℃ in an H2 atmosphere for 5min-15min to remove the oxide layer and adsorbed impurities on the surface of the substrate 100, thereby obtaining a clean and ordered surface of the substrate 100.

[0065] S2: Growth buffer layer 110 and stop layer 120

[0066] A buffer layer 110 is grown on the substrate 100 at a growth temperature of 650℃-750℃ and a growth thickness of 200nm-500nm; subsequently, a stop layer 120 is grown on the buffer layer 110 at a growth temperature of 650℃-750℃ and a growth thickness of 100nm-300nm.

[0067] S3: Growth of long-wavelength N-type semiconductor layer 130

[0068] A long-wavelength N-type semiconductor layer 130 is grown on the cutoff layer 120 at a growth temperature of 650℃-750℃ and a thickness of 500nm-1500nm. SiH4 is used as the N-type dopant with a doping concentration of 1×10⁻⁶. 17 / mm 3 -5×10 17 / mm 3 .

[0069] S4: Growth of long-wavelength multi-quantum-well layers 140

[0070] A long-wavelength multi-quantum-well layer 140 is grown on a long-wavelength N-type semiconductor layer 130 at a growth temperature of 600℃-700℃. An InGaAs / GaAs multi-quantum-well structure is grown with 3-8 quantum well periods, a well layer thickness of 6nm-10nm, and a barrier layer thickness of 10nm-20nm.

[0071] S5: Growing a wide-bandgap tunneling PN junction 150

[0072] Growing a wide-bandgap tunneling PN junction 150 on a long-wavelength multi-quantum-well layer 140 specifically includes the following sub-steps:

[0073] S51: A P-type buffer layer 151 is grown on a long-wavelength multi-quantum-well layer 140 using AlGaAs material. The growth temperature is 650℃-720℃, the thickness is 3nm-5nm, and the doping concentration is 1×10⁻⁶. 15 / mm 3 -1×10 17 / mm 3 The Al component accounts for 10%-20%;

[0074] S52: A heavily doped P-type layer 152 is grown on the P-type buffer layer 151 using AlGaAs material. The growth temperature is 650℃-720℃, the thickness is 5nm-20nm, and the doping concentration is 1×10⁻⁶. 16 / mm 3 -1×10 18 / mm 3 The Al component accounts for 25%-40%;

[0075] S53: A heavily doped N-type layer 153 is grown on a heavily doped P-type layer 152 using AlGaAs material. The growth temperature is 650℃-720℃, the thickness is 5nm-20nm, and the doping concentration is 2×10⁻⁶. 16 / mm 3 -1×10 17 / mm 3 The Al component accounts for 25%-40%;

[0076] S54: An N-type buffer layer 154 is grown on the heavily doped N-type layer 153. AlGaAs material is used, the growth temperature is 650℃-720℃, the thickness is 3nm-5nm, and the doping concentration is 2×10⁻⁶. 15 / mm 3 -1×10 16 / mm 3 The proportion of Al component is 10%-20%.

[0077] S6: Growth of short-wavelength multi-quantum-well layers

[0078] A short-wavelength multi-quantum-well layer 160 is grown on a wide-bandgap tunneling PN junction 150 at a growth temperature of 600℃-700℃. A GaInP / GaInP multi-quantum-well structure is grown with 3-8 quantum well periods, a well layer thickness of 5nm-8nm, and a barrier layer thickness of 8nm-15nm.

[0079] S7: Growth of short-wavelength P-type semiconductor layer 160

[0080] A short-wavelength P-type semiconductor layer 170 was grown on a short-wavelength multi-quantum-well layer 160 at a growth temperature of 650℃-750℃ and a thickness of 200nm-500nm. DEZn was used as the P-type dopant with a doping concentration of 1×10⁻⁶. 17 / mm 3 -5×10 17 / mm 3 .

[0081] All epitaxial layers were grown continuously in the same MOCVD equipment in one go. During the growth process, the reaction chamber pressure was controlled at 50 mbar-200 mbar, and the V / III ratio was 50-200. After growth, the reaction chamber temperature was lowered to room temperature, and the epitaxial wafer was removed.

[0082] The performance of the dual-band LED epitaxial wafer prepared in this embodiment was tested. After removing the substrate and fabricating electrodes, the wafer was tested under an injection current of 20 mA.

[0083] The peak wavelength of the short-wavelength (red light) is approximately 650nm-660nm, and the full width at half maximum (FWHM) is approximately 15nm-18nm; the peak wavelength of the long-wavelength (near-infrared) is approximately 940nm-960nm, and the FWHM is approximately 20nm-25nm; the dual-band optical output power ratio (red light / near-infrared) is approximately 1:0.8-1:1.2, with good spectral uniformity; the operating voltage (Vf) is approximately 2.8V-3.2V, and the leakage current (under -5V reverse bias) is less than 1μA, indicating that the 5%-15% interpenetrating channel ratio achieves the best balance between electrical conduction and optical transparency.

[0084] Example 2

[0085] This embodiment provides a dual-band LED epitaxial wafer with sapphire as the substrate, and both the long-wavelength and short-wavelength bands are InGaN / GaN multi-quantum-well structures.

[0086] The epitaxial wafer structure in this embodiment is basically the same as that in Embodiment 1, except that:

[0087] Substrate 100 is a sapphire substrate (Al2O3), and a low-temperature GaN nucleation layer (not shown) with a thickness of 20nm-50nm is also provided on the substrate;

[0088] Buffer layer 110 is a high-temperature GaN layer with a thickness of 1μm-3μm;

[0089] The cutoff layer 120 is an undoped GaN layer with a thickness of 100nm-300nm;

[0090] The long-wavelength N-type semiconductor layer 130 is a GaN layer with a doping concentration of 1×10⁻⁶. 18 / mm 3 -5×10 18 / mm 3 ;

[0091] The long-wavelength multi-quantum-well layer 140 is an InGaN / GaN multi-quantum-well structure with a peak wavelength of 500nm-540nm (green light band).

[0092] In the wide-bandgap tunneling PN junction 150, the heavily doped P-type layer 152 and P-type buffer layer 151 are Mg doped, and the heavily doped N-type layer 153 and N-type buffer layer 154 are Si doped. The materials are GaN or AlGaN. The proportion of interpenetrating channels in the wide-bandgap tunneling PN junction 150 per unit area is still controlled at 5%-15%.

[0093] The short-wavelength multi-quantum-well layer 160 is an InGaN / GaN multi-quantum-well structure with a peak wavelength of 430nm-470nm (blue light band).

[0094] The short-wavelength P-type semiconductor layer 170 is a GaN layer with a doping concentration of 1×10⁻⁶.18 / mm 3 -5×10 18 / mm 3 .

[0095] The difference between the peak wavelength of the long-wavelength multi-quantum well layer 140 and the peak wavelength of the short-wavelength multi-quantum well layer 160 is greater than 50 nm. In this embodiment, the difference between their peak wavelengths is approximately 60 nm to 100 nm.

[0096] The preparation method of this embodiment is basically the same as that of Example 1, except that: the high temperature heat treatment temperature of the substrate is 1000℃-1100℃, the growth temperature of each epitaxial layer is 750℃-1050℃, and the growth pressure is 100mbar-500mbar.

[0097] In practical use, the dual-band LED epitaxial wafer of this embodiment also removes the sapphire substrate and is configured in reverse (short-wavelength blue light at the bottom and long-wavelength green light at the top). Electrons are first injected into the short-wavelength multi-quantum-well layer 160 to emit blue light, and then injected into the long-wavelength multi-quantum-well layer 140 through the wide-bandgap tunneling PN junction 150 to emit green light, achieving synchronous emission of blue and green dual-bands. This structure can be applied to full-color display backlighting, plant lighting (blue light + green light combination), and other fields.

[0098] Example 3

[0099] This embodiment provides a dual-band LED epitaxial wafer, using the same GaAs substrate and material system as in Embodiment 1, but adjusting the In composition in the InGaAs quantum well layer and the In composition in the GaInP quantum well layer to adjust the long-wavelength peak wavelength to 1050nm-1100nm (short-wave infrared) and the short-wavelength peak wavelength to 730nm-780nm (deep red light), with a wavelength difference of more than 50nm.

[0100] This embodiment further expands the application scenarios of dual-band LEDs by adjusting the wavelength difference between the long-wavelength and short-wavelength bands. For example, it can be used in the combined application of infrared detection and red light indication, spectral analysis and other fields.

[0101] Comparative Example

[0102] To verify the technical effects of the present invention, the following comparative examples are provided:

[0103] Comparative Example 1: The difference from Example 1 is that the proportion of interpenetrating channels in the wide-bandgap tunneling PN junction is 3% (below the lower limit of 5%). Test results show that due to insufficient tunneling paths, the operating voltage rises to above 3.8V, and the upper long-wavelength luminescence intensity is only 30%-40% of that in Example 1, with a significant decrease in dual-band luminescence uniformity.

[0104] Comparative Example 2: The difference from Example 1 is that the proportion of interpenetrating channels in the wide-bandgap tunneling PN junction is 20% (higher than the upper limit of 15%). Test results show that the leakage current increases to over 10 μA (-5V reverse bias), and due to excessive interpenetration in the heavily doped region leading to roughening of the quantum well interface, the internal quantum efficiency decreases by about 25%, and the short-wavelength light extraction efficiency is significantly reduced.

[0105] Comparative Example 3: The difference from Example 1 is that no P-type buffer layer and N-type buffer layer were provided. Test results show that Al and Si atoms in the heavily doped layer directly diffuse into the adjacent multi-quantum-well layer, leading to deterioration of the quantum well interface and a decrease of more than 40% in the luminescence intensity of both bands.

[0106] The above comparative examples verify the criticality and necessity of the interpenetrating channel ratio of 5%-15% and the buffer layer setting in this invention.

Claims

1. A dual-band LED epitaxial wafer, characterized in that, The substrate (100) includes a buffer layer (110), a cutoff layer (120), a long-wavelength N-type semiconductor layer (130), a long-wavelength multi-quantum well layer (140), a wide-bandgap tunneling PN junction (150), a short-wavelength multi-quantum well layer (160), and a short-wavelength P-type semiconductor layer (170) disposed sequentially from bottom to top on the substrate (100). The wide-bandgap tunneling PN junction (150) consists of a heavily doped P-type layer (152) and a heavily doped N-type layer (153) from bottom to top. The proportion of interpenetrating channels in the wide-bandgap tunneling PN junction (150) per unit area is 5-15%.

2. The dual-band LED epitaxial wafer according to claim 1, characterized in that, The wide-bandgap tunneling PN junction (150) also includes a P-type buffer layer (151) located between the heavily doped P-type layer (152) and the long-wavelength multi-quantum well layer (140), and an N-type buffer layer (154) located between the heavily doped N-type layer (153) and the short-wavelength multi-quantum well layer (160).

3. The dual-band LED epitaxial wafer according to claim 1, characterized in that, The doping concentration of the heavily doped P-type layer (152) is 1×10⁻⁶. 16 / mm 3 -1×10 18 / mm 3 The thickness is 5nm-20nm; the doping concentration of the heavily doped N-type layer (153) is 2×10⁻⁶. 16 / mm 3 -1×10 17 / mm 3 The thickness is 5nm-20nm.

4. The dual-band LED epitaxial wafer according to claim 2, characterized in that, The doping concentration of the P-type buffer layer (151) is 1×10⁻⁶. 15 / mm 3 -1×10 17 / mm 3 The thickness is 3nm-5nm; the doping concentration of the N-type buffer layer (154) is 2×10⁻⁶. 15 / mm 3 -1×10 16 / mm 3 The thickness is 3nm-5nm.

5. The dual-band LED epitaxial wafer according to claim 1, characterized in that, The difference between the peak wavelength of the long-wavelength multi-quantum well layer (140) and the peak wavelength of the short-wavelength multi-quantum well layer (160) is greater than 50 nm.

6. The dual-band LED epitaxial wafer according to claim 1, characterized in that, The substrate (100) is a GaAs substrate, the long-wavelength multi-quantum well layer (140) is an InGaAs quantum well layer, and the short-wavelength multi-quantum well layer (160) is a GaInP quantum well layer.

7. The dual-band LED epitaxial wafer according to claim 6, characterized in that, The heavily doped P-type layer (152) and P-type buffer layer (151) are Al doped, and the Al composition ratio of the P-type buffer layer (151) is lower than that of the heavily doped P-type layer (152); the heavily doped N-type layer (153) and N-type buffer layer (154) are Si doped, and the Si doping ratio of the N-type buffer layer (154) is lower than that of the heavily doped N-type layer (153).

8. The dual-band LED epitaxial wafer according to claim 1, characterized in that, The substrate (100) is a sapphire substrate, and the long-wavelength multi-quantum well layer (140) and the short-wavelength multi-quantum well layer (160) are both InGaN / GaN multi-quantum well structures.

9. A method for fabricating a dual-band LED epitaxial wafer as described in any one of claims 1-8, characterized in that, Includes the following steps: S1: Place the substrate (100) in the MOCVD reaction chamber; S2: A buffer layer (110) and a stop layer (120) are grown sequentially on a substrate (100). S3: A long-wavelength N-type semiconductor layer (130) is grown on the cutoff layer (120). S4: A long-wavelength multi-quantum-well layer (140) is grown on a long-wavelength N-type semiconductor layer (130). S5: A wide-bandgap tunneling PN junction (150) is grown on a long-wavelength multi-quantum-well layer (140), wherein the proportion of interpenetrating channels in the wide-bandgap tunneling PN junction (150) per unit area is 5-15%; S6: A short-wavelength multi-quantum-well layer (160) is grown on a wide-bandgap tunneling PN junction (150). S7: A short-wavelength P-type semiconductor layer (170) is grown on a short-wavelength multi-quantum-well layer (160).

10. The method for preparing a dual-band LED epitaxial wafer according to claim 9, characterized in that, The growth of the wide-bandgap tunneling PN junction (150) in step S5 includes: sequentially growing a P-type buffer layer (151), a heavily doped P-type layer (152), a heavily doped N-type layer (153), and an N-type buffer layer (154); The doping concentration of the heavily doped P-type layer (152) is 1×10⁻⁶. 16 / mm 3 -1×10 18 / mm 3 The thickness is 5nm-20nm; the doping concentration of the heavily doped N-type layer (153) is 2×10⁻⁶. 16 / mm 3 -1×10 17 / mm 3 The thickness is 5nm-20nm; The doping concentration of the P-type buffer layer (151) is 1×10⁻⁶. 15 / mm 3 -1×10 17 / mm 3 The thickness is 3nm-5nm; the doping concentration of the N-type buffer layer (154) is 2×10⁻⁶. 15 / mm 3 -1×10 16 / mm 3 The thickness is 3nm-5nm.

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