Deep ultraviolet LED epitaxial structure with improved hole concentration in p-type hole injection layer

Abstract

The present invention discloses a deep ultraviolet LED epitaxial structure for increasing the hole concentration in a p-type hole injection layer. The structure comprises a substrate, an AlN buffer layer, an n-type doped AlGaN layer, an AlGaN multi-quantum well light-emitting region, an AlGaN electron blocking layer, a superlattice interface quantum dot structure p-type hole injection layer, and a p-type GaN ohmic contact layer. The superlattice interface quantum dot structure p-type hole injection layer comprises a p-type AlN superlattice barrier layer with multiple periods, a GaN quantum dot layer, and a p-type AlGaN superlattice well layer. The GaN quantum dot layer comprises a plurality of GaN quantum dots, and the plurality of GaN quantum dots are distributed at the interface between the p-type AlN superlattice barrier layer and the p-type AlGaN superlattice well layer. The present invention can effectively reduce the activation energy of Mg acceptors in a p-type hole injection layer with a high Al content, increase the hole concentration in the p-type hole injection layer, and thereby improve the carrier injection efficiency of the device.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor light-emitting devices, and in particular to a deep ultraviolet LED epitaxial structure for increasing the hole concentration of a p-type hole injection layer. Background Art

[0002] Deep UV LEDs (Light Emitting Diodes) have enormous application potential in many fields, such as water and air purification, UV medical treatment, sterilization and disinfection, and gas sensing. In particular, the impact of the COVID-19 pandemic has significantly increased consumer awareness of sterilization and disinfection, prompting explosive growth in the deep UV LED market. Furthermore, compared to traditional UV light sources such as mercury lamps, deep UV LEDs offer advantages such as small size, low power consumption, long life, and adjustable wavelength. With the gradual ban on the production and sale of mercury-containing UV light sources, the development and utilization of deep UV LEDs has presented a once-in-a-lifetime opportunity.

[0003] Due to the increasing market demand for deep ultraviolet LEDs, research on deep ultraviolet LEDs is now very popular. Currently, deep ultraviolet LEDs mainly use AlGaN as the main growth material, and the CVD epitaxial growth method is used to grow the required light-emitting structure. Figure 1 The typical AlGaN-based deep ultraviolet LED epitaxial structure of the prior art is as follows: Figure 1 As shown, the structure includes: substrate 101, AlN buffer layer 102, n-type doped Al u Ga 1-u N layer 103, Al x Ga 1-x N / A y Ga 1-y N multi-quantum well light-emitting area 104, Al z Ga 1-z N electron blocking layer 105, p-type doped Al v Ga 1-v N layer 106 and p-type GaN ohmic contact layer 107 .

[0004] At present, with the continuous breakthroughs in deep ultraviolet LED technology, although many deep ultraviolet related products have appeared on the market, there are still many technical bottlenecks that limit the application of AlGaN-based deep ultraviolet LEDs. Among them, the low carrier injection efficiency is one of the important factors leading to the low internal quantum efficiency (IQE) of deep ultraviolet LEDs. In AlGaN materials, with the increase of Al component, the doping efficiency of Si (n-type doping) and Mg (p-type doping) gradually decreases. The low doping efficiency leads to increased material resistivity, increased operating voltage, low hole injection efficiency, and electron leakage, which seriously affects the carrier injection efficiency of the device. In terms of improving the doping efficiency of n-type doping, it has been possible to effectively improve the doping efficiency of n-AlGaN (n-type doped Al) by optimizing growth conditions, pulse doping and other technical means. u Ga 1-u However, in terms of p-type doping, since the activation energy of Mg increases from 200meV (GaN) to 630meV (AlN), the activation of Mg acceptors in AlGaN materials, especially under high Al content conditions, is very difficult. This makes it difficult to increase the hole concentration in p-AlGaN, resulting in low carrier injection efficiency. This also seriously restricts the application of AlGaN-based deep ultraviolet LEDs in the market. Summary of the Invention

[0005] The purpose of the present invention is to provide a deep ultraviolet LED epitaxial structure with an increased hole concentration in a p-type hole injection layer, which can effectively reduce the activation energy of Mg acceptors in a high-Al component p-type hole injection layer, increase the hole concentration in the p-type hole injection layer, and thus improve the carrier injection efficiency of the device.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A deep ultraviolet LED epitaxial structure for increasing the hole concentration of a p-type hole injection layer, the epitaxial structure comprising a substrate, an AlN buffer layer, an n-type doped AlGaN layer, an AlGaN multi-quantum well light-emitting region, an AlGaN electron blocking layer, a superlattice interface quantum dot structure p-type hole injection layer, and a p-type GaN ohmic contact layer;

[0008] The AlN buffer layer is grown on the substrate; the n-type doped AlGaN layer is grown on the AlN buffer layer; the AlGaN multi-quantum well light-emitting region is grown on the n-type doped AlGaN layer; the AlGaN electron blocking layer is grown on the AlGaN multi-quantum well light-emitting region; the superlattice interface quantum dot structure p-type hole injection layer is grown on the AlGaN electron blocking layer; and the p-type GaN ohmic contact layer is grown on the superlattice interface quantum dot structure p-type hole injection layer.

[0009] The AlGaN multi-quantum well light-emitting region is a periodic multi-quantum well structure formed by alternating stacking of quantum well layers and quantum barrier layers;

[0010] The p-type hole injection layer of the superlattice interface quantum dot structure includes multiple periods of superlattice interface quantum dot structures; the superlattice interface quantum dot structure includes, from bottom to top, a p-type AlN superlattice barrier layer, a GaN quantum dot layer and a p-type AlGaN superlattice well layer; the GaN quantum dot layer includes multiple GaN quantum dots; the multiple GaN quantum dots are distributed at the interface between the p-type AlN superlattice barrier layer and the p-type AlGaN superlattice well layer, and the GaN quantum dots are partially buried in the p-type AlN superlattice barrier layer.

[0011] Optionally, the substrate is made of sapphire, Si, SiC, GaN or AlN.

[0012] Optionally, the n-type doped AlGaN layer includes Al u Ga 1-u N layers, where 20%≤u≤100%;

[0013] The growth temperature of the n-type doped AlGaN layer is 1000° C.-1400° C.; the thickness of the n-type doped AlGaN layer is 0.1 μm-3 μm.

[0014] Optionally, the AlGaN multi-quantum well light-emitting region includes Al x Ga 1-x N / A y Ga 1-y N, among which Al x Ga 1-x N is a quantum well layer with a thickness of 2nm-5nm, Al y Ga 1-y N is a quantum barrier layer with a thickness of 5nm-15nm, 20%≤x≤100%, 20%≤y≤100%, x<y;

[0015] The growth temperature of the AlGaN multi-quantum well light-emitting region is 800° C.-1400° C.; the light-emitting wavelength of the AlGaN multi-quantum well light-emitting region is less than or equal to 300 nm.

[0016] Optionally, the AlGaN multi-quantum well light-emitting region has M periodic quantum well structures, where 1≤M≤50, and M is a positive integer.

[0017] Optionally, the AlGaN electron blocking layer includes Al z Ga 1-z N, where 20% ≤ z ≤ 100%;

[0018] The AlGaN electron blocking layer is grown at a temperature of 900° C. to 1400° C. and is doped with Mg impurities. The AlGaN electron blocking layer has a thickness of 1 nm to 500 nm.

[0019] Optionally, the growth temperature of the p-type hole injection layer of the superlattice interface quantum dot structure is 900° C.-1300° C., and Mg impurity doping is used.

[0020] Optionally, the superlattice interface quantum dot structure p-type hole injection layer includes Q periods of superlattice interface quantum dot structure, wherein 1≤Q≤100, and Q is a positive integer.

[0021] Optionally, the p-type AlGaN superlattice well layer includes Al w Ga 1-w N, wherein 20%≤w≤100%; the p-type AlN superlattice barrier layer comprises AlN;

[0022] The thickness of the p-type AlGaN superlattice well layer is equal to the thickness of the p-type AlN superlattice barrier layer; the thickness is 1 nm-4 nm.

[0023] Optionally, the p-type GaN ohmic contact layer has a thickness of 1 nm-500 nm.

[0024] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0025] The deep ultraviolet LED epitaxial structure disclosed by the present invention improves the hole concentration of the p-type hole injection layer, and the p-type doping Al in the typical AlGaN-based deep ultraviolet LED epitaxial structure is v Ga 1-v The N layer is replaced by multiple periods of p-type AlN superlattice barrier layer, GaN quantum dot layer and p-type AlGaN superlattice well layer. By adopting AlN / AlGaN superlattice structure as p-type hole injection layer, GaN quantum dots are inserted at the interface of AlN and AlGaN. By utilizing the low activation energy of Mg impurity dopant in GaN, the activation energy of Mg impurity dopant in the overall high Al component p-type hole injection layer structure is reduced by GaN quantum dots, thereby effectively improving the doping efficiency of Mg impurities in the p-type hole injection layer of the superlattice interface quantum dot structure, increasing the hole concentration in the p-type hole injection layer, and thus improving the carrier injection efficiency of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 Schematic diagram of a typical AlGaN-based deep ultraviolet LED epitaxial structure in the prior art;

[0028] Figure 2 This is a structural diagram of an embodiment of a deep ultraviolet LED epitaxial structure for increasing the hole concentration of the p-type hole injection layer according to the present invention. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] The purpose of the present invention is to provide a deep ultraviolet LED epitaxial structure with an increased hole concentration in a p-type hole injection layer, which can effectively reduce the activation energy of Mg acceptors in a high-Al component p-type hole injection layer, increase the hole concentration in the p-type hole injection layer, and thus improve the carrier injection efficiency of the device.

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Figure 2 This is a structural diagram of an embodiment of a deep ultraviolet LED epitaxial structure for increasing the hole concentration of the p-type hole injection layer according to the present invention. Figure 2 As shown, this embodiment provides a deep ultraviolet LED epitaxial structure for improving the hole concentration of the p-type hole injection layer. The deep ultraviolet LED epitaxial structure for improving the hole concentration of the p-type hole injection layer includes a substrate 201, an AlN buffer layer 202, an n-type doped AlGaN layer 203, an AlGaN multi-quantum well light-emitting region 204, an AlGaN electron blocking layer 205, a superlattice interface quantum dot structure p-type hole injection layer 210 and a p-type GaN ohmic contact layer 209.

[0033] An AlN buffer layer 202 is grown on a substrate 201; an n-type doped AlGaN layer 203 is grown on the AlN buffer layer 202; an AlGaN multi-quantum well light-emitting region 204 is grown on the n-type doped AlGaN layer 203; an AlGaN electron blocking layer 205 is grown on the AlGaN multi-quantum well light-emitting region 204; a superlattice interface quantum dot structure p-type hole injection layer 210 is grown on the AlGaN electron blocking layer 205; and a p-type GaN ohmic contact layer 209 is grown on the superlattice interface quantum dot structure p-type hole injection layer 210.

[0034] The AlGaN multi-quantum well light emitting region 204 is a periodic multi-quantum well structure formed by alternating quantum well layers and quantum barrier layers. The AlGaN multi-quantum well light emitting region 204 has M periodic quantum well structures, where 1≤M≤50, and M is a positive integer.

[0035] The p-type hole injection layer 210 of the superlattice interface quantum dot structure includes Q periods of superlattice interface quantum dot structure (AlN-GaN-AlGaN superlattice interface quantum dot structure), where 1≤Q≤100, and Q is a positive integer; the superlattice interface quantum dot structure includes, from bottom to top, a p-type AlN superlattice barrier layer 206, a GaN quantum dot layer 207, and a p-type AlGaN superlattice well layer 208; the GaN quantum dot layer 207 includes a plurality of GaN quantum dots; the plurality of GaN quantum dots are distributed at the interface between the p-type AlN superlattice barrier layer 206 and the p-type AlGaN superlattice well layer 208, and the GaN quantum dots are partially buried in the p-type AlN superlattice barrier layer 206.

[0036] Specifically, the substrate 201 is made of sapphire, Si, SiC, GaN or AlN.

[0037] The n-type doped AlGaN layer (n-type AlGaN layer) 203 includes Al u Ga 1-u N, where 20%≤u≤100%. The growth temperature of the n-type doped AlGaN layer is 1000℃-1400℃. The thickness of the n-type doped AlGaN layer is 0.1μm-3μm. The n-type doped AlGaN layer can also be called n-type doped Al u Ga 1-u N layer (n-type Al u Ga 1-u N layers).

[0038] The AlGaN multi-quantum well light emitting region 204 includes Al x Ga 1-x N / A y Ga 1-y N, among which Al x Ga 1-xN is a quantum well layer with a thickness of 2nm-5nm, Al y Ga 1-y N is a quantum barrier layer with a thickness of 5nm-15nm. The well barrier layers are alternately stacked, 20%≤x≤100%, 20%≤y≤100%, and x<y. The growth temperature of the AlGaN multi-quantum well light-emitting region 204 is 800℃-1400℃. The light-emitting wavelength of the AlGaN multi-quantum well light-emitting region 204 is less than or equal to 300nm. The AlGaN multi-quantum well light-emitting region can also be called Al x Ga 1-x N / A y Ga 1-y N multiple quantum well light emitting area.

[0039] The AlGaN electron blocking layer 205 includes Al z Ga 1-z N, wherein 20%≤z≤100%. The AlGaN electron blocking layer is grown at a temperature of 900°C-1400°C and is doped with Mg impurities. The thickness of the AlGaN electron blocking layer 205 is 1nm-500nm. The AlGaN electron blocking layer can also be referred to as Al z Ga 1-z N electron blocking layer.

[0040] The growth temperature of the superlattice interface quantum dot structure p-type hole injection layer 210 is 900° C.-1300° C., and Mg impurity doping is used.

[0041] The p-type hole injection layer, composed of Q periods of AlN-GaN-AlGaN superlattice interface quantum dot structure, is grown at a temperature of 900°C-1300°C. From bottom to top, a p-type AlN superlattice barrier layer, a GaN quantum dot layer, and a p-type AlGaN superlattice well layer are grown sequentially. The p-type AlN superlattice barrier layer, the GaN quantum dot layer, and the p-type AlGaN superlattice well layer form a Q-period AlN-GaN-AlGaN superlattice interface quantum dot structure.

[0042] The p-type hole injection layer composed of Q periods of AlN-GaN-AlGaN superlattice interface quantum dot structure is obtained by repeating the AlN-GaN-AlGaN superlattice interface quantum dot structure including the p-type AlN superlattice barrier layer 206, the GaN quantum dot layer 207 and the p-type AlGaN superlattice well layer 208 Q times.

[0043] The number of GaN quantum dots in the GaN quantum dot layer 207 is K, where K is a positive integer and K≥1.

[0044] The p-type AlGaN superlattice well layer 208 includes Al w Ga 1-wN, wherein 20%≤w≤100%; the p-type AlN superlattice barrier layer 206 comprises AlN. The thickness of the p-type AlGaN superlattice well layer 208 is equal to that of the p-type AlN superlattice barrier layer 206, and is 1nm-4nm. The p-type AlGaN superlattice well layer may also be referred to as a p-type Al w Ga 1-w N superlattice well layer.

[0045] The thickness of the p-type GaN (p-GaN) ohmic contact layer 209 is 1 nm to 500 nm.

[0046] The deep ultraviolet LED epitaxial structure for improving the hole concentration of the p-type hole injection layer of the present invention designs an AlN / GaN / AlGaN superlattice interface quantum dot structure in the p-type hole injection layer. By adopting the AlN / AlGaN superlattice structure as the p-type hole injection layer, GaN quantum dots are inserted at the interface (interface) of the AlN and AlGaN (AlN / AlGaN) superlattice to form a multi-period AlN-GaN-AlGaN superlattice interface quantum dot structure (multi-period AlN / GaN / AlGaN), which mainly changes the structure of the typical p-type hole injection layer (p-AlGaN) in the prior art. An AlN / GaN / AlGaN superlattice interface quantum dot structure is designed in the p-type hole injection layer. First, it is easier to grow GaN in 3D on the AlN surface and form GaN quantum dots. Second, the change in the Al component will generate an electric field inside. Due to spontaneous polarization and piezoelectric polarization effects, the electric field will also cause band bending, which also promotes the ionization of Mg acceptor dopants. Third, by inserting GaN quantum dots, the valence band maximum of GaN can be used to increase the valence band maximum of the entire system, which is higher than that of AlN (about 0.7-0.8 eV higher), effectively shortening the distance between the system valence band maximum and the Mg acceptor (acceptor) energy level, reducing the activation energy of the Mg acceptor dopant (Mg acceptor activation energy), thereby allowing the acceptor impurities to ionize more holes and improving the doping efficiency of the Mg acceptor dopant. Therefore, the use of AlN / GaN / AlGaN superlattice interface quantum dot structure increases the hole concentration of the p-type hole injection layer, which is especially important for the p-type hole injection layer with an average Al composition higher than 60%, and is beneficial to improving the carrier injection efficiency of the device, thereby improving the internal quantum efficiency of the device.

[0047] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0048] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A deep ultraviolet LED epitaxial structure for increasing the hole concentration of a p-type hole injection layer, characterized in that: The epitaxial structure includes a substrate, an AlN buffer layer, an n-type doped AlGaN layer, an AlGaN multi-quantum well light-emitting region, an AlGaN electron blocking layer, a superlattice interface quantum dot structure p-type hole injection layer and a p-type GaN ohmic contact layer; The AlN buffer layer is grown on the substrate; the n-type doped AlGaN layer is grown on the AlN buffer layer; the AlGaN multi-quantum well light-emitting region is grown on the n-type doped AlGaN layer; the AlGaN electron blocking layer is grown on the AlGaN multi-quantum well light-emitting region; the superlattice interface quantum dot structure p-type hole injection layer is grown on the AlGaN electron blocking layer; and the p-type GaN ohmic contact layer is grown on the superlattice interface quantum dot structure p-type hole injection layer. The AlGaN multi-quantum well light-emitting region is a periodic multi-quantum well structure formed by alternating stacking of quantum well layers and quantum barrier layers; The p-type hole injection layer of the superlattice interface quantum dot structure includes multiple periods of superlattice interface quantum dot structures; the superlattice interface quantum dot structure includes, from bottom to top, a p-type AlN superlattice barrier layer, a GaN quantum dot layer and a p-type AlGaN superlattice well layer; the GaN quantum dot layer includes multiple GaN quantum dots; the multiple GaN quantum dots are distributed at the interface between the p-type AlN superlattice barrier layer and the p-type AlGaN superlattice well layer, and the GaN quantum dots are partially buried in the p-type AlN superlattice barrier layer.

2. The deep ultraviolet LED epitaxial structure for increasing the hole concentration of the p-type hole injection layer according to claim 1, characterized in that: The substrate is made of sapphire, Si, SiC, GaN or AlN.

3. The deep ultraviolet LED epitaxial structure for increasing the hole concentration of the p-type hole injection layer according to claim 1, characterized in that: The n-type doped AlGaN layer includes Al u Ga 1-u N, where 20%≤u≤100%; The growth temperature of the n-type doped AlGaN layer is 1000° C.-1400° C.; the thickness of the n-type doped AlGaN layer is 0.1 μm-3 μm.

4. The deep ultraviolet LED epitaxial structure for increasing the hole concentration of the p-type hole injection layer according to claim 1, characterized in that: The AlGaN multi-quantum well light-emitting region includes Al x Ga 1-x N / A y Ga 1-y N, among which Al x Ga 1-x N is a quantum well layer with a thickness of 2nm-5nm, Al y Ga 1-y N is a quantum barrier layer with a thickness of 5nm-15nm, 20%≤x≤100%, 20%≤y≤100%, x<y; The growth temperature of the AlGaN multi-quantum well light-emitting region is 800° C.-1400° C.; the light-emitting wavelength of the AlGaN multi-quantum well light-emitting region is less than or equal to 300 nm.

5. The deep ultraviolet LED epitaxial structure for increasing the hole concentration of the p-type hole injection layer according to claim 1, characterized in that: The AlGaN multi-quantum well light-emitting region has M periodic quantum well structures, wherein 1≤M≤50, and M is a positive integer.

6. The deep ultraviolet LED epitaxial structure for increasing the hole concentration of the p-type hole injection layer according to claim 1, characterized in that: The AlGaN electron blocking layer includes Al z Ga 1-z N, where 20% ≤ z ≤ 100%; The AlGaN electron blocking layer is grown at a temperature of 900° C. to 1400° C. and is doped with Mg impurities. The AlGaN electron blocking layer has a thickness of 1 nm to 500 nm.

7. The deep ultraviolet LED epitaxial structure for increasing the hole concentration of the p-type hole injection layer according to claim 1, characterized in that: The growth temperature of the p-type hole injection layer of the superlattice interface quantum dot structure is 900° C.-1300° C., and Mg impurity doping is used.

8. The deep ultraviolet LED epitaxial structure for increasing the hole concentration of the p-type hole injection layer according to claim 1, characterized in that: The superlattice interface quantum dot structure p-type hole injection layer includes Q periods of superlattice interface quantum dot structure, wherein 1≤Q≤100, and Q is a positive integer.

9. The deep ultraviolet LED epitaxial structure for increasing the hole concentration of the p-type hole injection layer according to claim 1, characterized in that: The p-type AlGaN superlattice well layer includes Al w Ga 1-w N, wherein 20%≤w≤100%; the p-type AlN superlattice barrier layer comprises AlN; The thickness of the p-type AlGaN superlattice well layer is equal to the thickness of the p-type AlN superlattice barrier layer; the thickness is 1 nm-4 nm.

10. The deep ultraviolet LED epitaxial structure for increasing the hole concentration of the p-type hole injection layer according to claim 1, characterized in that: The thickness of the p-type GaN ohmic contact layer is 1 nm-500 nm.

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