Multiband light emitting diode epitaxial structure and preparation method thereof
By employing a multi-quantum well structure and gradient In composition design in multi-band light-emitting diodes, the problem of emission wavelength variation with current was solved, achieving wavelength consistency and high-efficiency light emission, and improving crystal quality and color temperature stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-03-24
AI Technical Summary
The emission wavelength and color temperature of existing multi-band light-emitting diodes are easily affected by the driving current, resulting in color temperature drift and narrowing of the emission spectrum half-width. In addition, the traditional growth process leads to uneven temperature distribution on the substrate surface, which affects the wavelength uniformity within the chip.
A multi-quantum-well light-emitting layer structure is adopted, including green, cyan and blue light active regions that are periodically and alternately grown along the epitaxial direction. The In component content decreases along the epitaxial direction and is precisely regulated by TMIn pulse processing and control of NH3 flow rate. Combined with the barrier layer design of different materials, a gradient In component variation is formed.
It effectively reduces the blue shift amplitude, improves wavelength uniformity and luminous efficiency, reduces color temperature drift, and improves crystal quality and luminous uniformity.
Smart Images
Figure CN121728876A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of semiconductor optoelectronic devices, and in particular to a multi-band light emitting diode epitaxial structure and a preparation method thereof. BACKGROUND
[0002] Light emitting diodes (LEDs) have been widely used in the field of lighting. In order to obtain high-quality full-spectrum white light, the industry usually adopts an epitaxial structure with multi-band light emission, that is, a plurality of quantum well layers with different light emission wavelengths are arranged in the active region.
[0003] At present, this kind of multi-band quantum well structure more adopts a vertical stacking method with a more simplified process, and one of the more common stacking sequences is: along the epitaxial direction, the light emission wavelength of the quantum well decreases in turn. This design is mainly based on two considerations: one is the material growth process, the long-wave quantum well needs a higher In component content and a lower growth temperature, and growing before the short-wave quantum well is conducive to ensuring the crystal quality; the second is the electrical performance, placing the short-wave quantum well close to the P-type layer is considered to be helpful to improve the hole injection efficiency.
[0004] However, this traditional structure has a significant deficiency: the light emission wavelength and color temperature of the LED will drift with the change of the driving current. At a small current, light emission is mainly dominated by short waves close to the P-type layer; when the current increases, the long-wave quantum well away from the P-type layer contributes to an increase, resulting in a shift of the light emission peak and a change in the overall color temperature. Secondly, the long-wave quantum well needs a higher In component, and its quantum confinement Stark effect (QCSE) is more significant, and when the driving current increases, the blue shift is more significant, resulting in a narrowing of the light emission spectrum half-width. In addition, in the MOCVD process, the long-wave quantum well is implemented by reducing the growth temperature to increase the In component, because the thermal expansion coefficient of the GaN epitaxial layer and the Al2O3 substrate is severely mismatched, the wafer will be upwardly convex during the cooling process, thereby affecting the wavelength uniformity of the wafer due to the uneven distribution of the actual temperature on the substrate surface. SUMMARY
[0005] The present application aims to overcome the deficiencies of the prior art, and provides a multi-band light emitting diode epitaxial structure and a preparation method thereof, which can effectively reduce the blue shift amplitude, improve the wavelength consistency, and at the same time ensure a higher light emission efficiency.
[0006] In order to solve the above problems, the present application provides a multi-band light emitting diode epitaxial structure, which comprises a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress release layer, a multi-quantum well light emitting layer, an electron blocking layer and a P-type semiconductor layer which are sequentially stacked along the epitaxial direction. The multi-quantum well light emitting layer comprises a green light active region, a cyan light active region and a blue light active region which are sequentially and periodically alternately grown along the epitaxial direction. The green light active region comprises a green light barrier layer one, a green light InGaN layer and a green light barrier layer two which are sequentially stacked and grown along the epitaxial direction; The cyan light active region comprises a cyan light InGaN layer and a cyan light barrier layer which are sequentially stacked and grown along the epitaxial direction; The blue light active region comprises a blue light InGaN layer and a blue light barrier layer which are sequentially stacked and grown along the epitaxial direction; The green light InGaN layer, the cyan light InGaN layer and the blue light InGaN layer in a single growth cycle all have a decreasing In content along the epitaxial direction.
[0007] As an improvement of the above technical solution, the number of growth cycles of the multi-quantum well light emitting layer is 2-4; The green light active region has a light emitting wavelength of 511-565 nm; The cyan light active region has a light emitting wavelength of 470-490 nm; The blue light active region has a light emitting wavelength of 391-487 nm; The In content of the green light InGaN layer is 0.23-0.28; The In content of the cyan light InGaN layer is 0.18-0.22; The In content of the blue light InGaN layer is 0.05-0.17.
[0008] As an improvement of the above technical solution, the green light InGaN layer, the cyan light InGaN layer and the blue light InGaN layer are all made of InGaN material without intentional doping, and the In content linearly decreases along the epitaxial direction; wherein the difference between the maximum and minimum values of the In content is ≤0.04.
[0009] As an improvement of the above technical solution, the In content of the green light InGaN layer linearly decreases along the epitaxial direction, the decreasing gradient slope is 0.011 / nm-0.015 / nm, the growth thickness is 2.5-3.5 nm, and the growth temperature is 730-750℃; The In content of the cyan light InGaN layer linearly decreases along the epitaxial direction, the decreasing gradient slope is 0.008 / nm-0.01 / nm, the growth thickness is 2.5-3.5 nm, and the growth temperature is 730-750℃; The In content of the blue light InGaN layer linearly decreases along the epitaxial direction, the decreasing gradient slope is 0.003 / nm-0.007 / nm, the growth thickness is 2.5-3.5 nm, and the growth temperature is 730-750℃.
[0010] As the improvement of the above technical scheme, the green light InGaN layer needs to be treated by three TMIn pulse processes, the processing flow is 105-115 μmol / min, 95-105 μmol / min and 85-95 μmol / min respectively, the NH3 flow is 8.5-9.5 L / min, and the processing time is 1.1-1.4 s, 0.8-1.1 s and 0.8-1.1 s respectively; The cyan light InGaN layer needs to be treated by three TMIn pulse processes, the processing flow is 83-93 μmol / min, 75-85 μmol / min and 66-77 μmol / min respectively, the NH3 flow is 9.5-10.5 L / min, and the processing time is 0.7-1.0 s, 0.5-0.9 s and 0.5-0.9 s respectively; The blue light InGaN layer needs to be treated by three TMIn pulse processes, the processing flow is 53-63 μmol / min, 50-60 μmol / min and 47-57 μmol / min respectively, the NH3 flow is 11.5-12.5 L / min, and the processing time is 0.2-0.5 s, 0.2-0.5 s and 0.1-0.2 s respectively.
[0011] As the improvement of the above technical scheme, in the TMIn pulse process, the temperature of the TMIn source bottle is 20-25℃, the pressure is 750-850 torr, and N2 is used as the carrier gas to carry the saturated vapor of TMIn.
[0012] As the improvement of the above technical scheme, after a single TMIn pulse process, the mixed gas of N2 and NH3 needs to be introduced, and the introduction time is 1.5-2.3 s.
[0013] As the improvement of the above technical scheme, the green light barrier layer one and the green light barrier layer two are both made of InGaN material, the In component content is X, 0.005≤X≤0.02, and the growth thickness is 8-13 nm; The cyan light barrier layer is made of GaN material, and the growth thickness is 8-13 nm; The blue light barrier layer is made of AlGaN material, the Al component content is Y, 0.02≤Y≤0.05, and the growth thickness is 8-13 nm.
[0014] As the improvement of the above technical scheme, the buffer layer is made of GaN material without intentional doping, and the growth thickness is 20-30 nm; The N-type semiconductor layer is made of GaN material doped with Si element, the Si doping concentration is 3.5×10¹ 8 cm - ³~6.5×10¹ 8cm - ³, with a growth temperature of 900℃~1100℃ and a growth thickness of 1.5μm~3.0μm; The low-temperature stress relief layer comprises stress relief region InGaN layers and stress relief region GaN layers that are periodically and alternately grown along the epitaxial direction, with a period number of 3 to 8; the In content of the stress relief region InGaN layer is 0.01 to 0.04. The electron blocking layer is made of AlGaN material without intentional doping, and the growth thickness is 10nm~60nm; The thickness of the p-type semiconductor layer is 50 nm to 200 nm, and its doping concentration is 5 × 10⁻⁶. 19 cm - ³~1×10 21 cm - ³.
[0015] Accordingly, the present invention also provides a method for fabricating a multi-band light-emitting diode epitaxial structure, comprising the following steps: Provide a substrate; A buffer layer is deposited on the substrate; An N-type semiconductor layer is deposited on the buffer layer; A low-temperature stress relief layer is deposited on the N-type semiconductor layer; A multi-quantum-well light-emitting layer is deposited on the low-temperature stress-relieving layer; An electron blocking layer is deposited on the multi-quantum-well light-emitting layer; A P-type semiconductor layer is deposited on the electron blocking layer; The multi-quantum-well light-emitting layer includes green light-generating regions, cyan light-generating regions, and blue light-generating regions that are periodically and alternately grown along the epitaxial direction. The green light active region includes three layers of green light barrier layer one, green light InGaN layer and green light barrier layer two, which are grown sequentially along the epitaxial direction. The blue light active region includes a blue light InGaN layer and a blue light barrier layer that are sequentially stacked along the epitaxial direction; The blue light active region includes a blue light InGaN layer and a blue light barrier layer that are sequentially stacked along the epitaxial direction; In a single growth cycle, the In content of the green, cyan, and blue InGaN layers all decreases along the epitaxial direction.
[0016] The implementation of this invention has the following beneficial effects: (1) The multi-quantum-well light-emitting layer of the present invention includes a green active region, a cyan active region, and a blue active region that are periodically and alternately grown along the epitaxial direction; the green active region includes a green barrier layer one, a green InGaN layer, and a green barrier layer two that are stacked sequentially along the epitaxial direction; the cyan active region includes a cyan InGaN layer and a cyan barrier layer that are stacked sequentially along the epitaxial direction; the blue active region includes a blue InGaN layer and a blue barrier layer that are stacked sequentially along the epitaxial direction. The above-mentioned stacked structure effectively solves the problem that in traditional unidirectional stacking, charge carriers are preferentially injected into the InGaN quantum well layer near the P-type semiconductor layer. Under low-current operating conditions, the blue InGaN layer and the cyan InGaN layer near the P-type semiconductor layer dominate the light emission. As the driving current increases, the electric field penetration depth increases, and the underlying green InGaN layer is gradually activated, thereby achieving a dynamic balance of the emission contribution of each band under different current densities, which significantly alleviates the color temperature drift problem caused by the emission concentration on one side of the P-type semiconductor layer.
[0017] (2) In the green, cyan, and blue InGaN layers of a single growth cycle, the In content decreases along the epitaxial direction. The gradient change in In content alleviates the difference in lattice constant between high-In layers (such as the green InGaN layer) and low-In layers (such as the blue InGaN layer), reduces dislocation density and defect generation, improves the overall crystal integrity of the multi-quantum-well layer, and thus improves radiative recombination efficiency. The gradient In content weakens the built-in electric field strength in the InGaN quantum well, i.e., suppresses the quantum-confined Stark effect, reduces electron-hole wave function separation, enhances the probability of radiative recombination, and avoids luminous efficiency decay. The decreasing In content design promotes uniform injection of charge carriers in the multi-quantum-well layer, balances electron and hole concentrations, reduces non-radiative recombination, and improves internal quantum efficiency. By precisely controlling the In content gradient of each band, the green, cyan, and blue active regions work synergistically at low current densities, enhancing the full-spectrum white light output efficiency, improving the color rendering index, and reducing color temperature drift. Attached Figure Description
[0018] Fig. 1 This is a schematic diagram of the structure of a multi-band light-emitting diode epitaxial structure according to an embodiment of the present invention; Fig. 2 This is a schematic diagram of the structure of a multi-quantum well light-emitting layer according to an embodiment of the present invention. Detailed Implementation
[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.
[0020] See Figs. 1-2As shown, this embodiment of the invention provides a multi-band light-emitting diode epitaxial structure, including a substrate 100, a buffer layer 200, an N-type semiconductor layer 300, a low-temperature stress relief layer 400, a multi-quantum well light-emitting layer 500, an electron blocking layer 600, and a P-type semiconductor layer 700, which are sequentially stacked along the epitaxial direction.
[0021] It should be noted that the substrate 100 can be a sapphire substrate. Sapphire is currently the most commonly used substrate material. Sapphire substrates have the advantages of mature manufacturing process, low price, easy cleaning and processing, and good stability at high temperatures.
[0022] The buffer layer 200 is made of GaN material without intentional doping, and has a growth thickness of 20nm to 30nm. Examples of growth thicknesses are 20nm, 22nm, 27nm, and 30nm, but it is not limited to these.
[0023] The N-type semiconductor layer 300 is made of GaN material doped with Si, and the Si doping concentration is 3.5 × 10¹. 8 cm - ³~6.5×10¹ 8 cm - ³, with a growth temperature of 900℃~1100℃ and a growth thickness of 1.5μm~3.0μm.
[0024] The low-temperature stress relief layer 400 includes stress relief region InGaN layers and stress relief region GaN layers that are periodically and alternately grown along the epitaxial direction, with a period number of 3 to 8; the In content of the stress relief region InGaN layer is 0.01 to 0.04. The electron blocking layer 600 is made of AlGaN material without intentional doping, and has a growth thickness of 10nm~60nm; The P-type semiconductor layer 700 has a growth thickness of 50nm~200nm and a doping concentration of 5×10⁻⁶. 19 cm - ³~1×10 21 cm - ³.
[0025] Specifically, the multi-quantum-well light-emitting layer 500 includes green light-active regions 510, cyan light-active regions 520, and blue light-active regions 530 that are periodically and alternately grown along the epitaxial direction, with a period number of 2 to 4. For example, the period number is 2, 3, or 4.
[0026] The emission wavelength of the green light active region is 511nm~565nm; The emission wavelength of the cyan active region is 470nm~490nm; The emission wavelength of the blue light active region is 391nm~487nm; The In content of the green InGaN layer is 0.23~0.28; The In content of the bluish-green InGaN layer is 0.18~0.22; The In content of the blue light InGaN layer is 0.05~0.17.
[0027] Preferably, the green light active region 510 includes a green light barrier layer 1 511, a green light InGaN layer 512, and a green light barrier layer 2 513 that are sequentially stacked along the epitaxial direction. The blue light active region 520 includes a blue light InGaN layer 521 and a blue light barrier layer 522 that are sequentially stacked along the epitaxial direction. The blue light active region 530 includes a blue light InGaN layer 531 and a blue light barrier layer 532 that are sequentially stacked along the epitaxial direction. In a single growth cycle, the In content of the green InGaN layer 512, cyan InGaN layer 521, and blue InGaN layer 531 all decreases along the epitaxial direction.
[0028] The multi-quantum-well light-emitting layer 500 of this invention includes a green active region 510, a cyan active region 520, and a blue active region 530 that are periodically and alternately grown along the epitaxial direction. The green active region 510 includes a green barrier layer 511, a green InGaN layer 512, and a second green barrier layer 513 that are stacked sequentially along the epitaxial direction. The cyan active region 520 includes a cyan InGaN layer 521 and a cyan barrier layer 522 that are stacked sequentially along the epitaxial direction. The blue active region 530 includes a blue InGaN layer 531 and a blue barrier layer 532 that are stacked sequentially along the epitaxial direction. This stacked structure effectively solves the problem of carrier preferential injection into the InGaN quantum well layer closer to the P-type semiconductor layer in traditional unidirectional stacking. Under low-current operating conditions, the blue InGaN layer 531 and the cyan InGaN layer 521 closer to the P-type semiconductor layer dominate light emission. As the driving current increases, the electric field penetration depth increases, and the underlying green InGaN layer 512 is gradually activated, thereby achieving a dynamic balance of the emission contribution of each band under different current densities, which significantly alleviates the color temperature drift problem caused by the emission concentration on one side of the P-type semiconductor layer.
[0029] In a single growth cycle, the In content of the green InGaN layer 512, cyan InGaN layer 521, and blue InGaN layer 531 all decreases along the epitaxial direction. This gradient In content alleviates the lattice constant difference between high-In layers (e.g., green InGaN layer 512) and low-In layers (e.g., blue InGaN layer 531), reduces dislocation density and defect formation, and improves the overall crystal integrity of the multi-quantum-well emitting layer 500, thereby increasing radiative recombination efficiency. The gradient In content weakens the built-in electric field strength in the InGaN quantum wells, i.e., suppressing the quantum-confined Stark effect, reducing electron-hole wavefunction separation, enhancing the probability of radiative recombination, and preventing luminescence efficiency decay. The decreasing In content design promotes uniform carrier injection within the multi-quantum-well emitting layer 500, balances electron and hole concentrations, reduces non-radiative recombination, and improves internal quantum efficiency. By precisely controlling the In component gradient of each band, the green, cyan, and blue active regions work together at low current densities, enhancing the full-spectrum white light output efficiency, improving the color rendering index, and reducing color temperature drift.
[0030] Furthermore, the green InGaN layer 512, the cyan InGaN layer 521, and the blue InGaN layer 531 are all made of InGaN material without intentional doping, and the In content of each component decreases linearly along the epitaxial direction; wherein, the difference between the maximum and minimum values of the In content is ≤0.04, and the difference is exemplarily 0.01, 0.02, 0.03, and 0.04, but is not limited thereto.
[0031] A gradient variation of In composition ≤0.04 can significantly suppress In segregation in high-In regions, preventing the formation of nonradiative recombination centers caused by In-rich clusters and effectively reducing dislocation density. The small gradient variation allows for a smooth transition of the lattice constant difference between each luminescent InGaN layer and its corresponding barrier layer, reducing interfacial stress accumulation, preventing dislocations from extending into the active region, and improving crystal integrity. Furthermore, the narrow gradient design reduces carrier localization under high current density, effectively lowering the Auger recombination probability.
[0032] Ideally, the In content of the green InGaN layer 512 decreases linearly along the epitaxial direction, with a decreasing gradient slope of 0.011 / nm to 0.015 / nm. Examples of decreasing gradient slopes are 0.011, 0.012, 0.013, 0.014, and 0.015, but not limited to these. The growth thickness is 2.5nm to 3.5nm, and the growth temperature is 730℃ to 750℃. The In content of the cyan InGaN layer 521 decreases linearly along the epitaxial direction, with a gradient slope of 0.008 / nm to 0.01 / nm. Examples of gradient slopes are 0.008, 0.009, and 0.01, but not limited to these. The growth thickness is 2.5nm to 3.5nm, and the growth temperature is 730℃ to 750℃. The In content of the blue InGaN layer 531 decreases linearly along the epitaxial direction, with a gradient slope of 0.003 / nm to 0.007nm / nm. Examples of gradient slopes are 0.003, 0.004, 0.005, 0.006, and 0.007, but not limited to these. The growth thickness is 2.5nm to 3.5nm, and the growth temperature is 730℃ to 750℃.
[0033] The green InGaN layer 512 has the highest In content, therefore it uses the steepest gradient slope. The cyan InGaN layer 521 is next, while the blue InGaN layer 531 has the lowest In content and the weakest polarization effect, so it uses a relatively gentle gradient slope. This differentiated configuration of gradient slopes allows the built-in electric field formed within each emitting InGaN layer to accurately compensate for its own piezoelectric polarization field, thereby effectively suppressing the quantum confined Stark effect (QCSE) in different wavelength ranges and significantly reducing the blue shift of the emission peak under high current.
[0034] Optimally, the In content of the green InGaN layer 512 decreases linearly from 0.26 to 0.22 along the epitaxial direction, the In content of the cyan InGaN layer 521 decreases linearly from 0.22 to 0.19 along the epitaxial direction, and the In content of the blue InGaN layer 531 decreases linearly from 0.16 to 0.15 along the epitaxial direction.
[0035] It should be noted that the entire epitaxial structure is completed in an MOCVD device, and each light-emitting InGaN layer is grown within a uniform temperature range, which solves the problems of wafer warping and uneven surface temperature distribution caused by cooling in traditional variable temperature processes, and reduces the standard deviation of wavelength within the wafer.
[0036] By precisely controlling the combination of three key parameters—TMIn molar flow rate, NH3 flow rate, and TMIn pulse duration—independent and precise control of the In composition of quantum wells of different colors can be achieved without changing the temperature.
[0037] Specifically, the green InGaN layer 512 needs to undergo three TMI pulse treatments, with processing flow rates of 105~115 μmol / min, 95~105 μmol / min, and 85~95 μmol / min respectively, an NH3 flow rate of 8.5~9.5 L / min, and processing times of 1.1~1.4 s, 0.8~1.1 s, and 0.8~1.1 s respectively. The cyan InGaN layer 521 requires three TMI pulse treatments, with treatment flow rates of 83~93 μmol / min, 75~85 μmol / min, and 66~77 μmol / min respectively, an NH3 flow rate of 9.5~10.5 L / min, and treatment times of 0.7~1.0 s, 0.5~0.9 s, and 0.5~0.9 s respectively. The blue InGaN layer 531 requires three TMI pulse treatments, with processing flow rates of 53~63 μmol / min, 50~60 μmol / min, and 47~57 μmol / min, respectively, an NH3 flow rate of 11.5~12.5 L / min, and processing times of 0.2~0.5 s, 0.2~0.5 s, and 0.1~0.2 s, respectively.
[0038] The In composition gradient within a single luminescent InGaN layer is controlled by performing three consecutive TMIn pulse treatments within a single growth cycle. These three pulses create a stepped In supply, allowing In atoms to be orderly embedded layer by layer into the GaN lattice, preventing indium cluster aggregation under high In flux. Composition fluctuations are controlled within ±0.02, eliminating non-radiative recombination centers caused by indium-rich regions. The pulse interval (maintained by continuous NH3 injection) provides time for atomic rearrangement, reducing dislocations caused by lattice mismatch and effectively lowering the dislocation density at the quantum well interface.
[0039] More preferably, in the TMI pulse processing, the temperature of the TMI source bottle is 20°C to 25°C, and the pressure is 750 to 850 torr, with N2 as the carrier gas carrying the saturated vapor of TMI. Examples of temperatures include 20°C, 21°C, 23°C, and 25°C, but are not limited to these. Examples of pressures include 750 torr, 800 torr, 810 torr, 830 torr, and 850 torr, but are not limited to these.
[0040] Ideally, after each TMI pulse treatment, a mixture of N2 and NH3 should be introduced for 1.5–2.3 seconds. The rapid purging of residual TMI with N2 carrier gas, combined with the continuous supply of NH3, inhibits the formation of InN particles or carbon deposition from the TMI and residual gas, eliminating surface pits and defects. The continuous introduction of NH3 prevents nitrogen desorption from the GaN surface due to high temperatures, maintaining the stability of the NH bonds and providing uniform reaction sites for the next pulse.
[0041] More preferably, both the first green barrier layer 511 and the second green barrier layer 513 are made of InGaN material, with an In content of X, 0.005 ≤ X ≤ 0.02, and a growth thickness of 8~13 nm; X is exemplarily 0.005, 0.01, 0.012, 0.15, 0.02, but is not limited thereto. The growth thickness is exemplarily 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, but is not limited thereto. Growing green barrier layers made of InGaN material containing trace amounts of In on both sides and at intervals of the green InGaN layer 512 helps to reduce the lattice mismatch between the green InGaN layer 512 and the green barrier layer, reduce interface defects, and at the same time moderately increase the valence band barrier height, improving hole localization.
[0042] The cyan barrier layer 522 is made of GaN material with a growth thickness of 8-13 nm. Exemplary growth thicknesses include 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, and 13 nm, but are not limited to these. Using pure GaN as the cyan barrier layer 522 provides high conduction and valence band barriers, effectively limiting electron-hole recombination within the cyan InGaN layer. Simultaneously, its excellent crystal quality helps maintain high internal quantum efficiency in the cyan wavelength band.
[0043] The blue light barrier layer 532 is made of AlGaN material with an Al content of Y of 0.02 ≤ Y ≤ 0.05 and a growth thickness of 8~13 nm. Examples of Y values are 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, and 0.05, but it is not limited to these. Examples of growth thicknesses are 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, and 13 nm, but it is not limited to these. The introduction of Al components into the blue light barrier layer 532 significantly increases the electron barrier height, effectively suppressing electron overflow, and ensuring the stability of the luminous efficiency of the blue quantum well, especially under high current density.
[0044] Accordingly, the present invention also provides a method for fabricating a multi-band light-emitting diode epitaxial structure, characterized by comprising the following steps: Provide a substrate 100; A buffer layer 200 is deposited on the substrate 100; An N-type semiconductor layer 300 is deposited on the buffer layer 200; A low-temperature stress relief layer 400 is deposited on the N-type semiconductor layer 300; A multi-quantum-well light-emitting layer 500 is deposited on the low-temperature stress-relieving layer 400; An electron blocking layer 600 is deposited on the multi-quantum-well light-emitting layer 500; A P-type semiconductor layer 700 is deposited on the electron blocking layer 600; The multi-quantum-well light-emitting layer 500 includes a green light-generating active region 510, a cyan light-generating active region 520, and a blue light-generating active region 530 that are periodically and alternately grown along the epitaxial direction. The green light active region 510 includes green light barrier layer 1 511, green light InGaN layer 512, and green light barrier layer 2 513, which are sequentially stacked along the epitaxial direction. The blue light active region 520 includes a blue light InGaN layer 521 and a blue light barrier layer 522 that are sequentially stacked along the epitaxial direction. The blue light active region 530 includes a blue light InGaN layer 531 and a blue light barrier layer 532 that are sequentially stacked along the epitaxial direction. In a single growth cycle, the In content of the green InGaN layer 512, cyan InGaN layer 521, and blue InGaN layer 531 all decreases along the epitaxial direction.
[0045] The following specific embodiments will provide further explanation.
[0046] Example 1 This embodiment provides a multi-band light-emitting diode epitaxial structure, including a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress relief layer, a multi-quantum-well light-emitting layer, an electron blocking layer, and a P-type semiconductor layer sequentially stacked along the epitaxial direction; The multi-quantum-well light-emitting layer includes green light-generating regions, cyan light-generating regions, and blue light-generating regions that are periodically and alternately grown along the epitaxial direction, with a period number of 3. The green light active region includes three layers of green light barrier layer one, green light InGaN layer and green light barrier layer two, which are grown sequentially along the epitaxial direction. The green light barrier layer is made of InGaN material with an In content of 0.01 and a growth thickness of 10 nm. The green InGaN layer is made of InGaN material without intentional doping, and its In content decreases linearly from 0.26 to 0.22 along the epitaxial direction. The growth thickness is 3 nm and the growth temperature is 740 °C. The green InGaN layer needs to be processed by three TMI pulses, with flow rates of 110 μmol / min, 100 μmol / min, and 90 μmol / min respectively, an NH3 flow rate of 9.0 L / min, and processing times of 1.2 s, 1.0 s, and 1.0 s respectively. The second green barrier layer is made of InGaN material with an In content of 0.018 and a growth thickness of 12 nm. The blue light active region includes a blue light InGaN layer and a blue light barrier layer that are sequentially stacked along the epitaxial direction; The cyan InGaN layer is made of InGaN material without intentional doping, and its In content decreases linearly from 0.22 to 0.19 along the epitaxial direction. The growth thickness is 3 nm and the growth temperature is 740 °C. The cyan InGaN layer needs to be treated with three TMI pulses, with flow rates of 85 μmol / min, 80 μmol / min, and 72 μmol / min respectively, an NH3 flow rate of 10.0 L / min, and treatment times of 0.9 s, 0.8 s, and 0.8 s respectively. The cyan barrier layer is made of GaN material and has a growth thickness of 10.5 nm; The blue light active region includes a blue light InGaN layer and a blue light barrier layer that are sequentially stacked along the epitaxial direction; The blue light InGaN layer is made of InGaN material without intentional doping, and its In content decreases linearly from 0.16 to 0.15 along the epitaxial direction. The growth thickness is 3 nm and the growth temperature is 740 °C. The blue InGaN layer needs to undergo three TMI pulse treatments, with processing flow rates of 58 μmol / min, 55 μmol / min, and 52 μmol / min respectively, an NH3 flow rate of 12 L / min, and processing times of 0.3 s, 0.3 s, and 0.2 s respectively. The blue light barrier layer is made of AlGaN material with an Al content of 0.035 and a growth thickness of 10 nm. In the TMI pulse processing, the temperature of the TMI source bottle is 25°C and the pressure is 800 torr, with N2 as the carrier gas to carry the saturated vapor of TMI. After each TMIn pulse treatment, a mixture of N2 and NH3 gas needs to be introduced for 2.0 seconds.
[0047] Example 2 The difference between this embodiment and Embodiment 1 is that: The green InGaN layer is made of InGaN material without intentional doping, and its In content decreases linearly from 0.28 to 0.23 along the epitaxial direction; The bluish-green InGaN layer is made of InGaN material without intentional doping, and its In content decreases linearly from 0.22 to 0.18 along the epitaxial direction; The blue light InGaN layer is made of InGaN material without intentional doping, and its In content decreases linearly from 0.17 to 0.11 along the epitaxial direction.
[0048] Example 3 The difference between this embodiment and Embodiment 1 is that: The green InGaN layer is made of InGaN material without intentional doping, and its In content decreases linearly from 0.28 to 0.24 along the epitaxial direction; The bluish-green InGaN layer is made of InGaN material without intentional doping, and its In content decreases linearly from 0.22 to 0.18 along the epitaxial direction; The blue light InGaN layer is made of InGaN material without intentional doping, and its In content decreases linearly from 0.17 to 0.13 along the epitaxial direction.
[0049] Example 4 The difference between this embodiment and Embodiment 1 is that: The green InGaN layer needs to undergo three TMI pulse treatments, with processing flow rates of 105 μmol / min, 95 μmol / min, and 85 μmol / min respectively, an NH3 flow rate of 8.5 L / min, and processing times of 1.1 s, 0.8 s, and 0.8 s respectively. The cyan InGaN layer needs to be treated with three TMI pulses, with flow rates of 83 μmol / min, 75 μmol / min, and 66 μmol / min respectively, an NH3 flow rate of 9.5 L / min, and treatment times of 0.7 s, 0.5 s, and 0.5 s respectively. The blue InGaN layer needs to undergo three TMI pulse treatments, with processing flow rates of 53 μmol / min, 50 μmol / min, and 47 μmol / min respectively, an NH3 flow rate of 11.5 L / min, and processing times of 0.2 s, 0.2 s, and 0.1 s respectively.
[0050] Example 5 The difference between this embodiment and Embodiment 1 is that: The green InGaN layer needs to be processed by three TMI pulses, with processing flow rates of 115 μmol / min, 105 μmol / min, and 95 μmol / min respectively, an NH3 flow rate of 9.5 L / min, and processing times of 1.4 s, 1.1 s, and 1.1 s respectively. The cyan InGaN layer needs to be treated with three TMI pulses, with flow rates of 93 μmol / min, 85 μmol / min, and 77 μmol / min respectively, an NH3 flow rate of 10.5 L / min, and treatment times of 1.0 s, 0.9 s, and 0.9 s respectively. The blue InGaN layer needs to undergo three TMI pulse treatments, with processing flow rates of 63 μmol / min, 60 μmol / min, and 57 μmol / min respectively, an NH3 flow rate of 12.5 L / min, and processing times of 0.5 s, 0.5 s, and 0.2 s respectively.
[0051] Example 6 The difference between this embodiment and Embodiment 1 is that: Both the first and second green light barrier layers are made of InGaN material without intentional doping, with an In content of 0.02 and a growth thickness of 13 nm. The cyan barrier layer is made of GaN material and has a growth thickness of 13 nm. The blue light barrier layer is made of AlGaN material with an Al content of 0.05% and a growth thickness of 13 nm.
[0052] Example 7 The difference between this embodiment and Embodiment 1 is that: Both the first and second green light barrier layers are made of InGaN material without intentional doping, with an In content of 0.005 and a growth thickness of 8 nm. The cyan barrier layer is made of GaN material and has a growth thickness of 8 nm. The blue light barrier layer is made of AlGaN material with an Al content of 0.02 and a growth thickness of 8 nm.
[0053] Comparative Example 1 This comparative example provides a light-emitting diode epitaxial structure, including a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress relief layer, a multi-quantum-well light-emitting layer, an electron blocking layer, and a P-type semiconductor layer sequentially stacked along the epitaxial direction; The multi-quantum-well light-emitting layer has a periodic structure of alternating InGaN multi-quantum-well layers and GaN quantum barrier layers, with a stacking period of 8. Within a single period, the InGaN quantum well layer has an In composition of 0.17, and the thickness of the InGaN quantum well layer is 3.4 nm; the thickness of the GaN quantum barrier layer is 13 nm.
[0054] Comparative Example 2 The difference between this comparative example and Example 1 is as follows: The green InGaN layer has an In content of 0.24 and does not require three TMIn pulse processing. The In composition content of the cyan InGaN layer is 0.21, and it does not require three TMIn pulse treatments; The blue InGaN layer has an In content of 0.15 and does not require three TMIn pulse processing steps.
[0055] The light-emitting diode epitaxial structures of Examples 1 to 7 and Comparative Examples 1 to 2 were fabricated into LED chips with a size of 10mil × 14mil. The luminous efficacy improvement, WD STD (nm) and XRD test results of the epitaxial wafers (002)arcsec and (102)arcsec were obtained by testing the chips under a current of 10mA. The luminous efficacy improvement was calculated based on Comparative Example 1.
[0056] It should be noted that arcsec(002) data can characterize screw dislocations, while arcsec(102) data can characterize mixed dislocations of screw and edge dislocations. The smaller the value of arcsec(002) or arcsec(102), the lower the dislocation density and the better the crystal quality. WD STD mainly reflects the wavelength standard deviation. The smaller the standard deviation, the more concentrated the chip parameter distribution and the more stable the manufacturing process.
[0057] The test results are shown in the table below:
[0058] The light-emitting diode epitaxial structures of Examples 1 to 7 and Comparative Examples 1 to 2 were fabricated into LED chips with a size of 10mil × 14mil, and their blue shift was tested at currents of 5mA, 10mA, and 20mA.
[0059] The test results are shown in the table below:
[0060] As can be seen from the above test results, the In content of the green, cyan, and blue InGaN layers in a single growth cycle all decreases along the epitaxial direction. The gradient change in In content alleviates the difference in lattice constant between high-In and low-In layers, reduces dislocation density and defect formation, improves the overall crystal integrity of the multi-quantum-well layer, and thus enhances the radiative recombination efficiency.
[0061] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.
Claims
1. A multi-band light-emitting diode epitaxial structure, characterized in that, It includes a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress relief layer, a multi-quantum-well light-emitting layer, an electron blocking layer, and a P-type semiconductor layer, which are sequentially stacked along the epitaxial direction; The multi-quantum-well light-emitting layer includes green light-generating regions, cyan light-generating regions, and blue light-generating regions that are periodically and alternately grown along the epitaxial direction. The green light active region includes three layers of green light barrier layer one, green light InGaN layer and green light barrier layer two, which are grown sequentially along the epitaxial direction. The blue light active region includes a blue light InGaN layer and a blue light barrier layer that are sequentially stacked along the epitaxial direction; The blue light active region includes a blue light InGaN layer and a blue light barrier layer that are sequentially stacked along the epitaxial direction; In a single growth cycle, the In content of the green, cyan, and blue InGaN layers all decreases along the epitaxial direction.
2. The multi-band light-emitting diode epitaxial structure as described in claim 1, characterized in that, The growth cycle number of the multi-quantum-well light-emitting layer is 2 to 4; The emission wavelength of the green light active region is 511nm~565nm; The emission wavelength of the cyan active region is 470nm~490nm; The emission wavelength of the blue light active region is 391nm~487nm; The In content of the green InGaN layer is 0.23~0.28; The In content of the bluish-green InGaN layer is 0.18~0.22; The In content of the blue light InGaN layer is 0.05~0.
17.
3. The multi-band light-emitting diode epitaxial structure as described in claim 1 or 2, characterized in that, The green, cyan, and blue InGaN layers are all made of InGaN material without intentional doping, and the In content decreases linearly along the epitaxial direction; wherein the difference between the maximum and minimum In content is ≤0.
04.
4. The multi-band light-emitting diode epitaxial structure as described in claim 3, characterized in that, The In content of the green InGaN layer decreases linearly along the epitaxial direction, with a gradient slope of 0.011 / nm to 0.015 / nm, a growth thickness of 2.5nm to 3.5nm, and a growth temperature of 730℃ to 750℃. The In content of the bluish InGaN layer decreases linearly along the epitaxial direction, with a gradient slope of 0.008 / nm to 0.01 / nm, a growth thickness of 2.5nm to 3.5nm, and a growth temperature of 730℃ to 750℃. The In content of the blue InGaN layer decreases linearly along the epitaxial direction, with a gradient slope of 0.003 / nm to 0.007nm / nm, a growth thickness of 2.5nm to 3.5nm, and a growth temperature of 730℃ to 750℃.
5. The multi-band light-emitting diode epitaxial structure as described in claim 4, characterized in that, The green InGaN layer requires three TMI pulse treatments, with flow rates of 105~115 μmol / min, 95~105 μmol / min, and 85~95 μmol / min, respectively, an NH3 flow rate of 8.5~9.5 L / min, and treatment times of 1.1~1.4 s, 0.8~1.1 s, and 0.8~1.1 s, respectively. The cyan InGaN layer needs to undergo three TMI pulse treatments, with treatment flow rates of 83~93 μmol / min, 75~85 μmol / min, and 66~77 μmol / min respectively, an NH3 flow rate of 9.5~10.5 L / min, and treatment times of 0.7~1.0 s, 0.5~0.9 s, and 0.5~0.9 s respectively. The blue InGaN layer needs to undergo three TMI pulse treatments, with processing flow rates of 53~63 μmol / min, 50~60 μmol / min, and 47~57 μmol / min respectively, an NH3 flow rate of 11.5~12.5 L / min, and processing times of 0.2~0.5 s, 0.2~0.5 s, and 0.1~0.2 s respectively.
6. The multi-band light-emitting diode epitaxial structure as described in claim 5, characterized in that, In the TMI pulse processing, the temperature of the TMI source bottle is 20℃~25℃ and the pressure is 750~850 torr, with N2 as the carrier gas to carry the saturated vapor of TMI.
7. The multi-band light-emitting diode epitaxial structure as described in claim 5, characterized in that, After each TMIn pulse treatment, a mixture of N2 and NH3 gas needs to be introduced for 1.5 to 2.3 seconds.
8. The multi-band light-emitting diode epitaxial structure as described in claim 1, characterized in that, Both the first and second green light barrier layers are made of InGaN material, with an In content of X, 0.005≤X≤0.02, and a growth thickness of 8~13nm. The cyan barrier layer is made of GaN material and has a growth thickness of 8~13nm; The blue light barrier layer is made of AlGaN material, with an Al component content of Y of 0.02≤Y≤0.05 and a growth thickness of 8~13nm.
9. The multi-band light-emitting diode epitaxial structure as described in claim 1, characterized in that, The buffer layer is made of GaN material without intentional doping, and has a growth thickness of 20nm~30nm. The N-type semiconductor layer is made of GaN material doped with Si, with a Si doping concentration of 3.5 × 10¹. 8 cm - ³~6.5×10¹ 8 cm - ³, with a growth temperature of 900℃~1100℃ and a growth thickness of 1.5μm~3.0μm; The low-temperature stress relief layer comprises stress relief region InGaN layers and stress relief region GaN layers that are periodically and alternately grown along the epitaxial direction, with a period number of 3 to 8; the In content of the stress relief region InGaN layer is 0.01 to 0.
04. The electron blocking layer is made of AlGaN material without intentional doping, and the growth thickness is 10nm~60nm; The thickness of the p-type semiconductor layer is 50 nm to 200 nm, and its doping concentration is 5 × 10⁻⁶. 19 cm - ³~1×10 21 cm - ³.
10. A method for fabricating a multi-band light-emitting diode epitaxial structure as described in any one of claims 1 to 9, characterized in that, Includes the following steps: Provide a substrate; A buffer layer is deposited on the substrate; An N-type semiconductor layer is deposited on the buffer layer; A low-temperature stress relief layer is deposited on the N-type semiconductor layer; A multi-quantum-well light-emitting layer is deposited on the low-temperature stress-relieving layer; An electron blocking layer is deposited on the multi-quantum-well light-emitting layer; A P-type semiconductor layer is deposited on the electron blocking layer; The multi-quantum-well light-emitting layer includes green light-generating regions, cyan light-generating regions, and blue light-generating regions that are periodically and alternately grown along the epitaxial direction. The green light active region includes three layers of green light barrier layer one, green light InGaN layer and green light barrier layer two, which are grown sequentially along the epitaxial direction. The blue light active region includes a blue light InGaN layer and a blue light barrier layer that are sequentially stacked along the epitaxial direction; The blue light active region includes a blue light InGaN layer and a blue light barrier layer that are sequentially stacked along the epitaxial direction; In a single growth cycle, the In content of the green, cyan, and blue InGaN layers all decreases along the epitaxial direction.