Algan-based deep ultraviolet light emitting diode injection structure and application

Abstract

This invention discloses an AlGaN-based deep ultraviolet light-emitting diode injection structure and its application. The injection structure provided by this invention is a periodic structure, and each periodic structure includes the following components: p-Al with a gradually changing Al component proportion. m Ga 1‑m N layers; in each periodic structure, the proportion of Al component m gradually changes linearly from x to y along the growth direction, with x ranging from 0.6 to 0.85 and y ranging from 0.3 to 0.7, and x > y. The injection structure provided by this invention can utilize the negatively polarized body charge induced by the piezoelectric effect to modulate the energy band of the p-type region, reduce the hole injection barrier, and suppress electron leakage. This method integrates the p-type region of the deep ultraviolet light-emitting device into a unified periodic structure, avoiding the use of an electron blocking layer (p-EBL), improving the device carrier injection efficiency while effectively reducing the device operating voltage, which is of great significance for improving the electro-optical conversion efficiency of AlGaN-based DUV-LEDs and promoting their industrial applications.

Description

Technical Field

[0001] This invention belongs to the field of deep ultraviolet light-emitting diode technology, specifically relating to an injection structure of an AlGaN-based deep ultraviolet light-emitting diode (DUV-LED) and its application. Background Technology

[0002] AlGaN-based deep ultraviolet light-emitting diodes (DUV-LEDs), as a solid-state light source, have significant advantages such as no mercury pollution, small size, low power consumption, long lifespan, and easy integration. They play an irreplaceable role in many fields such as sterilization and disinfection, environmental monitoring, communication detection, and medical and health care, and are one of the core industries with great development prospects in the group III nitride semiconductor field.

[0003] However, the industrialization process of DUV-LED is currently facing the bottleneck of low electro-optical conversion efficiency. One of the main reasons for the difficulty in improving its performance is the non-equilibrium carrier injection caused by the electron blocking layer (p-EBL) and the high operating voltage of the device. These are also key technical problems that urgently need to be solved at this stage.

[0004] Due to their small effective mass and high drift velocity, excess electrons can easily escape from the quantum well into the p-type region after radiative recombination with holes. To suppress electron leakage, high-Al composition AlGaN is typically used as a p-EBL layer between the DUV-LED quantum well and the p-type region. Its wide bandgap creates a high potential barrier in the conduction band, effectively blocking electrons. However, the presence of the p-EBL also presents challenges. Firstly, the high potential barrier in the valence band poses a significant challenge to hole injection into the quantum well, leading to a severe imbalance in electron and hole transport. Secondly, the large bandgap of the p-EBL introduces an additional voltage drop between it, the quantum well, and the p-AlGaN, resulting in an increased device operating voltage and ultimately affecting the performance of the DUV-LED.

[0005] Currently, there are two main technical solutions to address the above problems: One is to optimize the configuration of the p-EBL by modulating the band structure through piezoelectric polarization, thereby reducing the hole injection barrier or increasing the probability of hole tunneling through the EBL while ensuring that the p-EBL suppresses electron leakage. The other feasible solution is to achieve high-concentration effective doping of high-Al-content p-AlGaN through polarization-induced doping or superlattice methods, enabling p-AlGaN to participate in device operation as a hole supply layer (replacing traditional p-GaN), thus reducing the band hierarchy between the p-EBL and the hole supply layer and lowering the hole injection barrier.

[0006] Clearly, while the two technical approaches mentioned above can optimize the carrier transport characteristics of the device to some extent, they cannot fundamentally eliminate the blocking of holes by p-EBL, the low carrier injection efficiency, and the high operating voltage caused by the band structure. Therefore, the improvement in device performance is very limited. Summary of the Invention

[0007] To address the above problems, this invention provides a p-AlGaN integrated structure with periodically varying composition. This structure avoids the use of p-EBL, significantly reduces device operating voltage while improving carrier injection efficiency, thereby improving the electro-optical conversion efficiency of DUV-LEDs. This solves the problems of low carrier injection efficiency and high device operating voltage caused by EBL.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] In a first aspect, the present invention provides an injection structure for an AlGaN-based deep ultraviolet light-emitting diode, which is a periodic structure, each periodic structure comprising the following components: p-Al with a gradually changing Al component ratio. m Ga 1-m N layers;

[0010] In each periodic structure, the proportion of Al component m gradually changes linearly from x to y along the growth direction, with x ranging from 0.6 to 0.85, preferably from 0.65 to 0.8; y ranging from 0.3 to 0.7, preferably from 0.45 to 0.65; and x > y.

[0011] In the above-mentioned injection structure, the thickness of each periodic structure is 'a', and the value of 'a' ranges from 3 to 10 nm, preferably from 4 to 8 nm.

[0012] In the above-mentioned injection structure, the thickness of the structure is n·a, where n represents the number of cycles, and the value of n ranges from 2 to 20, preferably from 5 to 15.

[0013] Secondly, the present invention further provides a method for fabricating the injection structure of the above-mentioned AlGaN-based deep ultraviolet light-emitting diode, comprising the following steps:

[0014] S1: The flow rates of the Ga source and Al source are adjusted to their initial values ​​using the metal-organic chemical vapor deposition (MOCVD) method.

[0015] S2: Open the organic source gas path for epitaxial growth. By controlling the gradual gradient of the flow rates of the Ga and Al sources, p-Al with a linearly gradual change in the Al component ratio is grown on the AlGaN-based quantum well sample. m Ga 1-m The N-layer, which represents the first cycle of completing the integrated structure;

[0016] S3: Close the organic source gas path and adjust the flow rates of Ga source and Al source to the initial values ​​in step S1;

[0017] S4: Repeat steps S2-S3 to obtain p-Al with linearly gradual changes in Al composition of the periodic structure. m Ga 1-m N-integrated structure.

[0018] In step S1, the flow rates of the Ga source and Al source are controlled in proportion to meet the requirements of x and y in the above periodic structure.

[0019] In step S2, the linear relationship of the proportion of Al component in the above periodic structure is satisfied by controlling the gradual change ratio of the flow rate of the Al source.

[0020] In step S2, the thickness a of the aforementioned periodic structure is satisfied by controlling the growth time.

[0021] In step S4, the number of repetitions is controlled to meet the requirement of the number of periods n of the above-mentioned periodic structure.

[0022] In the above preparation method, the number of repetitions, film thickness, and Al composition gradient are selected according to the requirements of the AlGaN-based deep ultraviolet light-emitting diode device, and the condition y is satisfied. <x。

[0023] Thirdly, the present invention further provides an AlGaN-based deep ultraviolet light-emitting diode device, which includes the above-mentioned injection structure of the AlGaN-based deep ultraviolet light-emitting diode.

[0024] For example, the AlGaN-based deep ultraviolet light-emitting diode device includes, from bottom to top, the following structure:

[0025] Sapphire substrate;

[0026] AlN layer;

[0027] AlN / AlGaN multi-period stress modulation layer;

[0028] n-AlGaN layer;

[0029] AlGaN / AlGaN active region layer;

[0030] Periodic Al composition-gradient p-AlGaN integrated structure;

[0031] p-GaN layer.

[0032] The beneficial effects achieved by this invention are as follows:

[0033] 1. This invention employs a p-AlGaN integrated structure with periodically varying composition, which serves the dual purpose of blocking electrons and promoting the longitudinal transport of holes, thereby avoiding the use of p-EBL and eliminating the working voltage caused by p-EBL while improving the longitudinal transport capability of charge carriers.

[0034] In terms of carrier transport, this invention introduces a piezoelectric polarization effect through a gradual change in Al composition, inducing negatively polarized body charges inside p-AlGaN to modulate the energy band: on the one hand, it raises the conduction band, forming a continuous high barrier, which suppresses electron leakage and thus replaces p-EBL; on the other hand, the negatively polarized charge can also effectively lower the energy level of the valence band, so that holes only need to cross a small barrier during transport from the p-type region to the active region and are not blocked by p-EBL, thus greatly improving the injection efficiency.

[0035] In terms of operating voltage, this structure integrates the p-type region, which simplifies the device configuration, eliminates the band gradient introduced by p-EBL in traditional DUV-LEDs, and reduces the operating voltage.

[0036] 2. The periodically component-gradient p-AlGaN integrated structure provided by this invention has a simple structure, no strict requirements on the gradient, thickness and number of periods, low growth requirements, and is easy to achieve in growth. It is suitable for ultraviolet light-emitting devices of various wavelengths, has good applicability and practicality, and is suitable for widespread application in the industrialization of deep ultraviolet light-emitting devices. Attached Figure Description

[0037] Figure 1 This diagram illustrates the gradual change in the proportion of Al component during the growth of the periodically varying p-AlGaN integrated structure provided by the present invention.

[0038] Figure 2 This is a schematic diagram of the full structure of the DUV-LED with a p-AlGaN integrated structure containing periodic component gradients, as provided in Example 2.

[0039] Figure 3 The simulation results of the internal quantum efficiency and power density of the DUV-LED with a periodically varying p-AlGaN integrated structure provided in Example 2 are shown in the figure.

[0040] Figure 4 The simulation verification results of the current-voltage (IV) curves of the DUV-LED with a p-AlGaN integrated structure containing periodic component gradients provided in Example 2 are shown in the figure. Detailed Implementation

[0041] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0042] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods. Unless otherwise specified, the reagents, materials, instruments, etc. used in the following examples can all be obtained from commercial channels.

[0043] The present invention specifically provides a periodically composition-graded p-AlGaN integrated structure for AlGaN-based deep ultraviolet light-emitting devices, and its preparation method specifically includes the following steps:

[0044] S1: Using the method of metalorganic chemical vapor deposition (MOCVD), adjust the flow rates of the metal sources (Ga source and Al source) to the initial values, corresponding to an AlGaN film with an Al component of x. x Ga 1-x N film;

[0045] S2: Open the organic source gas path for epitaxial growth. By controlling the flow rates of the metal sources, grow a p-AlGaN layer with a linearly gradually decreasing Al component from x to y on the AlGaN-based quantum well sample as the first period of the integrated structure, with a thickness of a. The Al component y can be adjusted by adjusting the growth parameters, but it needs to satisfy the condition y < x; as Figure 1 shown;

[0046] S3: Close the organic source gas path and adjust the metal source flow rate to the initial value in S1;

[0047] S4: Repeat S2 - S3 (n - 1) times to obtain a composition-graded p-AlGaN integrated structure with a period number of n.

[0048] The key of the present invention lies in using the periodically Al-component-graded p-AlGaN to integrate the p-type region, avoiding the use of p-EBL, simplifying the device configuration, improving the carrier injection efficiency of DUV-LED and reducing the working voltage.

[0049] Different Al component gradient, thickness and period number have different improvement effects on the carrier transport ability and working voltage. The present invention can control the Al component gradient, single-period thickness and period number of the p-type integrated structure by controlling the metal source flow rate, growth time and cycle number, so as to modulate the energy band structure and carrier transport behavior of the p-type region.

[0050] In this invention, the core element is the use of a periodically varying Al composition to enable the p-type region to simultaneously block electrons and promote hole transport, thereby weakening and replacing the function of the p-EBL. By introducing a negatively polarized body charge through piezoelectric polarization, a continuous high barrier is formed in the p-type conduction band region, suppressing electron leakage and thus replacing the p-EBL. In this structure, hole injection is no longer blocked by the p-EBL, and the height of the p-type valence band barrier is reduced under the modulation of the polarization charge, significantly improving hole transport capability. Simultaneously, this integrated structure eliminates the band structure introduced by the p-EBL, thereby reducing the operating voltage.

[0051] In summary, this invention integrates the p-type region by setting p-AlGaN with periodically varying Al composition, avoiding the use of p-EBL, greatly improving the carrier transport capability of AlGaN-based DUV-LEDs, and effectively reducing the device operating voltage, thereby improving the electro-optical conversion efficiency of the device.

[0052] Example 1: p-AlGaN integrated structure with periodic component gradient and its preparation

[0053] This embodiment provides a p-AlGaN integrated structure with periodically varying composition, the preparation method of which includes:

[0054] S1: Using metal-organic chemical vapor deposition (MOCVD), the flow rates of the metal sources (Ga source and Al source) are adjusted to their initial values, corresponding to an AlGaN material with a composition of 0.8 (i.e., Al). 0.8 Ga 0.2 N);

[0055] S2: Open the organic source gas path for epitaxial growth. By controlling the flow rate of the metal source, a p-AlGaN layer with an Al composition that is linearly gradient from 0.8 to 0.55 is grown on the AlGaN-based quantum well sample as the first period of the integrated structure with a thickness of 6 nm.

[0056] S3: Close the organic source gas path and adjust the metal source flow rate to the initial value in S1;

[0057] S4: Repeat S2-S3 7 times to obtain a component-gradient p-AlGaN integrated structure with 8 periods.

[0058] Example 2: Fabrication of DUV-LEDs with periodically varying p-AlGaN integrated structures

[0059] like Figure 2 As shown, this embodiment provides a method for fabricating a DUV-LED with a periodically varying p-AlGaN integrated structure, comprising:

[0060] S1: A 2 μm thick AlN layer was grown on a sapphire substrate using MOCVD.

[0061] S2: An AlN / AlGaN stress modulation layer with 100 cycles is grown on the AlN layer;

[0062] S3: Growing a 1μm thick Si-doped Al layer on a superlattice stress buffer layer 0.55 Ga 0.45 Layer N is an n-type layer;

[0063] S4: In n-type Al 0.55 Ga 0.45 A 10nm thick Al layer is grown on the N layer. 0.5 Ga 0.5 N layers, serving as the first layer of the quantum barrier;

[0064] S5: A 2nm thick Al layer is grown on the quantum barrier. 0.35 Ga 0.65 The N-layer serves as a quantum well layer;

[0065] S6: Repeat S4-S5 4 times to obtain 5 pairs of quantum wells;

[0066] S7: Repeat S4 as the last quantum barrier to complete the growth of the active region;

[0067] S8: Adjust the flow rates of the metal sources (Ga source and Al source) to correspond to AlGaN material with a composition of 0.8 (i.e., Al). 0.8 Ga 0.2 N);

[0068] S9: Open the organic source gas path and grow a p-AlGaN layer with an Al composition that is linearly gradient from 0.8 to 0.55 on the AlGaN-based quantum well sample by controlling the flow rate of the metal source. This layer serves as the first period of the integrated structure and has a thickness of 6 nm.

[0069] S10: Close the organic source gas path and adjust the metal source flow rate to the initial value in S8;

[0070] S11: Repeat S9-S10 7 times to complete the growth of the component-gradient p-AlGaN integrated structure with a cycle number of 8.

[0071] S12: A 10 nm thick Mg-doped p-GaN layer is grown on the p-type integrated structure as the top ohmic contact layer.

[0072] Effect verification

[0073] Using a conventional DUV-LED structure containing p-EBL and constant composition p-AlGaN as a comparative example, the difference between it and the DUV-LED structure obtained in Example 2 is that the AlGaN / AlGaN active region layer and the p-GaN layer are respectively: p-EBL layer and constant composition p-AlGaN layer.

[0074] The AlGaN-based DUV-LED structure obtained in Example 2 and the DUV-LED structure containing p-EBL and constant composition p-AlGaN were compared and tested using simulation methods. The results are as follows:

[0075] (1) As Figure 3 As shown, the current density is 0-100 A / cm². 2 At that time, the maximum internal quantum efficiency of the AlGaN-based DUV-LED obtained in Example 2 increased by 29.7% compared to the conventional structure;

[0076] (2) Figure 3 As shown, the current density is 0-100 A / cm². 2 At that time, the maximum light output power density of the AlGaN-based DUV-LED obtained in Example 2 increased by 37.0% compared with the conventional structure.

[0077] (3) Figure 4 As shown, the current density is 100 A / cm². 2 In Example 2, the operating voltage of the AlGaN-based DUV-LED was reduced by 0.4V compared to the conventional structure.

[0078] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for fabricating an injection structure for an AlGaN-based deep ultraviolet light-emitting diode, characterized in that, The injection structure is a periodic structure, and each periodic structure includes the following components: p-Al with a gradually changing proportion of Al component. m Ga 1-m N layers; In each periodic structure, the proportion of Al component m changes linearly from x to y along the growth direction, with x ranging from 0.6 to 0.85 and y ranging from 0.3 to 0.7, and x > y. The thickness of each periodic structure is a, and the value of a ranges from 3 to 10 nm; The thickness of the injection structure is n·a; n represents the number of cycles, and the value of n ranges from 2 to 20; The method for preparing the injection structure includes the following steps: S1: The flow rates of the Ga source and Al source are adjusted to their initial values ​​using the metal-organic chemical vapor deposition method. S2: Open the organic source gas path for epitaxial growth. By controlling the gradual gradient of the flow rates of the Ga and Al sources, p-Al with a linearly gradual change in the Al component ratio is grown on the AlGaN-based quantum well sample. m Ga 1-m The N-layer, which represents the first cycle of completing the integrated structure; S3: Close the organic source gas path and adjust the flow rates of Ga source and Al source to the initial values ​​in step S1; S4: Repeat steps S2-S3 to obtain p-Al with linearly gradual changes in Al composition of the periodic structure. m Ga 1-m N-integrated structure; in: In step S1, the flow rate ratios of the Ga source and Al source are controlled to meet the requirements of x and y in each periodic structure. In step S2, the requirement of linear relationship of Al component proportion in each periodic structure is met by controlling the gradual change ratio of the Al source flow rate. In step S2, the thickness a of each periodic structure is required by controlling the growth time. In step S4, the number of repetitions is controlled to meet the requirement of the number of cycles n for each periodic structure.

2. The preparation method according to claim 1, characterized in that, In each periodic structure of the injection structure, x ranges from 0.65 to 0.8, y ranges from 0.45 to 0.65, a ranges from 4 to 8 nm, and n ranges from 5 to 15.

Images