Deep ultraviolet LED based on AlN / GaN digital alloy structure

Abstract

The invention discloses a deep ultraviolet LED (light-emitting diode) based on an AlN / GaN digital alloy structure. The deep ultraviolet LED structurally comprises a substrate; an n-type injection layer; a multi-quantum well active layer; a p-type electron blocking layer; a p-type injection layer; a p-type GaN layer; wherein the p-type injection layer is of a periodic digital alloy structure in which GaN and AlN grow alternately. According to the deep ultraviolet LED epitaxial structure, a GaN / AlN digital alloy structure is adopted to replace a traditional high-Al-component p-type injection layer, the activation energy of an acceptor of the p-type injection layer is reduced, the hole concentration can be improved, and the radiation recombination efficiency of carriers in an active region is remarkably improved by combining the structural design of multiple quantum wells.

Description

A deep ultraviolet LED based on AlN / GaN digital alloy structure Technical Field

[0001] This invention relates to a deep ultraviolet LED based on an AlN / GaN digital alloy structure, belonging to the field of semiconductor optoelectronic device technology. Background Technology

[0002] The development of semiconductor technology has always been intertwined with advancements in controllable doping technology. Breakthroughs in controllable doping technology are fundamental to realizing core structures such as pn junctions and pin junctions, thereby supporting the research and application of a series of optoelectronic devices such as light-emitting diodes (LEDs), laser diodes (LDs), and photodetectors. Among group III nitride semiconductors, AlGaN-based ultraviolet (UV) light-emitting devices, due to their advantages such as long lifespan, high efficiency potential, environmental friendliness, and portability, are gradually becoming an ideal replacement for traditional mercury UV lamps, and have broad application prospects in UV curing, phototherapy, disinfection, and sterilization.

[0003] Depending on the aluminum composition, AlGaN-based ultraviolet LEDs can cover the full ultraviolet spectrum range of 210-360 nm. Among them, aluminum-rich AlGaN with an aluminum composition of more than 50% is the core material for preparing deep ultraviolet (especially UVC band, 100-280 nm) LEDs. Its development is in line with the requirements of the Minamata Convention for the replacement of mercury lamps, and the market size continues to expand.

[0004] Wall penetration efficiency (WPE) is a core indicator for evaluating the performance of ultraviolet (UV) LEDs. Its value is closely related to the emission wavelength and mainly depends on four key aspects: radiation efficiency, light extraction efficiency, carrier injection efficiency, and electrical efficiency. Currently, the peak wall penetration efficiency of 275 nm UV LEDs has reached 15.3%, but there is still a significant gap compared to GaN-based visible LEDs. Furthermore, in the deep ultraviolet band below 250 nm and the UVB band, the wall penetration efficiency drops sharply. This performance bottleneck is closely related to the doping efficiency of aluminum-rich AlGaN and has become a core issue restricting the improvement of UV LED performance and its industrial application. Summary of the Invention

[0005] The purpose of this invention is to provide a deep ultraviolet LED based on an AlN / GaN digital alloy structure.

[0006] The objective of this invention is achieved through the following technical solution: a deep ultraviolet LED based on an AlN / GaN digital alloy structure, the structure of which, from bottom to top, comprises: a substrate; an n-type injection layer; a multi-quantum-well active layer; a p-type electron blocking layer; a p-type injection layer; and a p-type GaN layer; wherein the p-type injection layer is a periodic digital alloy structure in which GaN and AlN are grown alternately.

[0007] Preferably, in the p-type implanted layer, the number of GaN atomic layers per cycle is 1-10 monolayers, the number of AlN atomic layers is 1-10 monolayers, the number of cycles is 5-50, and at least one of GaN and AlN is doped with Mg atoms at a concentration of 1×10⁻⁶. 19 -10×10 19 cm -3 In other words, the doping of the p-type implantation layer can be divided into three types: both GaN and AlN are doped, only GaN is doped, and only AlN is doped.

[0008] Preferably, the n-type implanted layer is n-AlGaN with an Al composition of 0.5-0.8 and a silicon doping ion concentration of 1×10⁻⁶. 19 -10×10 19 cm -3 The thickness is 100-500nm.

[0009] Preferably, the active layer of the multi-quantum well is AlGaN, wherein the well layer thickness is 1-5 nm, the Al composition is 0.4-0.6, the barrier layer thickness is 10-20 nm, the Al composition is 0.5-1, and the number of periods is 2-4.

[0010] The p-type electron blocking layer is p-AlGaN, with an Al composition of 0.5-1 and a Mg ion concentration of 1×10⁻⁶. 19 -10×10 19 cm -3 The thickness is 5-10nm.

[0011] Preferably, the thickness of the p-type GaN layer is 10-50 nm, and the Mg ion concentration is 1×10⁻⁶. 19 - 10×10 19 cm -3 .

[0012] Preferably, the substrate is an AlN single crystal substrate or an AlN / sapphire template.

[0013] The deep ultraviolet (DUV) LED epitaxial wafer proposed in this invention employs a digital alloy structure to replace the traditional p-type injection layer. It utilizes the GaN / AlN interface barrier to restrict hole transport paths, preferentially accumulating holes in the multi-quantum-well (QW5) and reducing hole leakage to the p-region. Simultaneously, the multi-quantum-well structural design significantly improves the active region carrier radiative recombination efficiency. Test results show that under high injection conditions exceeding 5.5 A, the output power of this device is significantly superior to that of the traditional structure, with a marked improvement in the power spectral density and carrier radiative recombination rate within the quantum wells. This provides a new approach for the industrial application of high-performance DUV LEDs. Attached Figure Description

[0014] Figure 1 is a schematic diagram of the structure of a prior art deep ultraviolet LED epitaxial wafer (single layer) as shown in Comparative Example 1.

[0015] Figure 2 is a schematic diagram of the deep ultraviolet LED (digital alloy) based on the AlN / GaN digital alloy structure of the present invention.

[0016] Figure 3 shows the IV diagrams of two DUV LED epitaxial wafers with different structures.

[0017] Figure 4 shows the curve of output power of epitaxial wafer as a function of current.

[0018] Figure 5 shows the power spectral density within quantum wells of epitaxial wafers with different structures.

[0019] Figure 6 shows the radiative recombination rate of carriers in the quantum well. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Comparative Example 1 shows an existing deep ultraviolet LED epitaxial wafer, as shown in Figure 1. Its structure, from bottom to top, includes: an AlN substrate; an n-type injection layer; a multi-quantum-well active layer; a p-type electron blocking layer; a p-type injection layer; and a p-type GaN layer; wherein the n-type emitter layer is n-Al. 0.5 Ga 0.5 N, with a thickness of 100 nm and a silicon doping concentration of 5 × 10⁻⁶ 19 cm -3The active layer of the multi-quantum well has 3 periods, with a well layer thickness of 1 nm and an Al composition of 0.5%, and a barrier layer thickness of 9 nm and an Al composition of 0.7%. The p-type electron blocking layer is p-AlGaN with an Al composition of 0.9% and a doping concentration of 1 × 10⁻⁶. 19 cm -3 The thickness is 5 nm; the p-type emitter layer is p-AlGaN with an Al composition of 0.7 and a doping concentration of 1×10⁻⁶. 19 cm -3 The thickness is 100 nm; the thickness of the p-type GaN layer is 20 nm, and the doping concentration is 1×10⁻⁶. 19 cm -3 Example

[0022] A deep ultraviolet LED based on an AlN / GaN digital alloy structure, as shown in Figure 2, has a structure that is basically the same as that of Comparative Example 1. The difference lies in that the p-type injection layer is a periodic digital alloy structure with alternating growth of GaN and AlN. The thickness of GaN in each period is 10 nm, and GaN is 1 × 10⁻⁶ nm through Mg doping. 19 cm -3 The doping concentration is [value missing], the thickness of AlN is 10 nm, the number of periods is 5, and the total thickness is 100 nm.

[0023] Simulations were performed on the devices of Comparative Example 1 and Example 1, and the results are shown in Figures 3-6. Figure 3 shows the IV diagrams of two DUV LED devices with different structures. It can be seen that the turn-on voltage of the digital alloy structure device tends to increase. The structural change of the device affects the carrier injection efficiency and limits the carrier transport, which is the main reason for the increase in the device turn-on voltage. Figure 4 shows the output power of the device as a function of current. When the current is higher than 5.5A, the output power of the digital alloy structure device is significantly higher than that of the traditional AlGaN structure at the same current. Figure 5 analyzes the power spectral density in the quantum well of different structure devices. The power spectral density of the digital alloy structure is much greater than that of the comparative structure. In the device using the digital alloy structure, when electrons are injected from the n-type region into the active region, they are blocked by the high potential barrier quantum barrier, causing most electrons to be confined in QW5 and undergo radiative recombination. The radiative recombination of carriers in the quantum well and the leakage of electrons to the p-region in the device are then analyzed. Figure 6 shows the radiative recombination rate of carriers in the quantum well. When using a conventional AlGaN structure, the carrier concentration within the quantum wells is low, resulting in relatively low radiative recombination rates in each well. In contrast, DUV LEDs with digital alloy structures exhibit higher radiative recombination efficiencies. Therefore, using delta-doped DUV LEDs with digital alloy structures can effectively improve device performance.

[0024] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A deep ultraviolet LED based on an AlN / GaN digital alloy structure, the structure comprising, from bottom to top: a substrate; an n-type injection layer; a multi-quantum-well active layer; a p-type electron blocking layer; a p-type injection layer; and a p-type GaN layer; characterized in that... The p-type injection layer is a periodic digital alloy structure with alternating GaN and AlN growth.

2. The deep ultraviolet LED according to claim 1, characterized in that... The number of GaN atomic layers in each period of the p-type implanted layer is 1-10, the number of AlN atomic layers is 1-10, the number of periods is 5-50, and at least one of GaN and AlN is doped with Mg atoms at a concentration of 1×10⁻⁶. 19 -10×10 19 cm -3 .

3. The deep ultraviolet LED according to claim 1, characterized in that... The n-type implanted layer is n-AlGaN with an Al composition of 0.5-0.8% and a silicon doping concentration of 1×10⁻⁶. 19 -10×10 19 cm -3 The thickness is 100-500nm.

4. The deep ultraviolet LED according to claim 1, characterized in that... The active layer of the multi-quantum well is AlGaN, wherein the well layer thickness is 1-5 nm and the Al composition is 0.4-0.6, the barrier layer thickness is 10-20 nm and the Al composition is 0.5-1, and the number of periods is 2-4.

5. The deep ultraviolet LED according to claim 1, characterized in that... The p-type electron blocking layer is p-AlGaN, with an Al composition of 0.5-1 and a Mg ion concentration of 1×10⁻⁶. 19 -10×10 19 cm -3 The thickness is 5-10nm.

6. The deep ultraviolet LED according to claim 1, characterized in that... The p-type GaN layer has a thickness of 10-50 nm and a Mg ion concentration of 1×10⁻⁶. 19 - 10×10 19 cm -3 .

7. The deep ultraviolet LED according to claim 1, characterized in that... The substrate is an AlN single crystal substrate or an AlN / sapphire template.

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