CN212209532U

CN212209532U - LED epitaxial thin film with InGaN/GaN/AlGaN/GaN quantum well

Info

Publication number: CN212209532U
Application number: CN201921989929.6U
Authority: CN
Inventors: 李国强; 李媛; 洪晓松; 王文樑; 邢志恒
Original assignee: South China University of Technology SCUT
Current assignee: South China University of Technology SCUT
Priority date: 2019-11-18
Filing date: 2019-11-18
Publication date: 2020-12-22
Anticipated expiration: 2029-11-18

Abstract

The utility model discloses a LED epitaxial thin film with InGaN/GaN/AlGaN/GaN quantum well. The LED epitaxial film comprises n-GaN, and an InGaN/GaN/AlGaN/GaN quantum well, an electronic barrier layer and a p-GaN layer which are prepared by MOCVD and sequentially grow on the n-GaN. The utility model provides a near ultraviolet LED epitaxial thin film of high internal quantum efficiency has simple structure, efficient, can effectively improve the characteristics of quantum well material quality, but wide application in fields such as near ultraviolet, blue light, yellow green light LED.

Description

LED epitaxial thin film with InGaN/GaN/AlGaN/GaN quantum well

Technical Field

The utility model relates to an adopt the LED field of InGaN trap, concretely relates to LED epitaxial thin film with InGaN/GaN/AlGaN/GaN quantum well.

Background

With the rapid development of Light Emitting Diode (LED) technology, the light emitting band of LED has been widely applied to commercial products from green to ultraviolet, and in recent years, the broad application prospect of short wavelength ultraviolet LED (UV-LED) is continuously explored by people, attracting many people to shift the research focus to it. The ultraviolet LED is widely applied to the fields of white light solid-state lighting, optical storage, printing ink printing, water and air purification, biomedicine, environmental protection and the like. Because the ultraviolet LED has the characteristics of small volume, simple structure, high speed, adjustable wavelength, high energy, long service life, energy conservation, environmental protection and the like, compared with an ultraviolet mercury lamp, the ultraviolet LED has many advantages, is hopeful to replace the existing mercury lamp to become an ultraviolet light source of the next generation, and has huge social and economic values.

The ultraviolet light is divided into a total of three bands: UV-A (400-320nm), UV-B (320-280nm) and UV-C (280-200 nm). Among the uv LEDs, the near uv LEDs with wavelengths greater than 365nm that use InGaN as the well are currently being developed more rapidly. The quantum well of the near ultraviolet LED mostly adopts a multi-period InGaN/GaN structure, but because the difference of potential barriers of GaN and InGaN is small, the limiting capability of the GaN barrier on carriers is weak, so that the density of the carriers in the quantum well is low, and radiation recombination of the LED is not facilitated. In order to solve the problem of weak carrier confinement capability, another commonly used quantum well structure is an InGaN/AlGaN structure. Compared with a GaN barrier, the AlGaN barrier has higher potential barrier and enhanced carrier confinement capability. InGaN/AlGaN structures, however, also present two problematic issues. On one hand: spontaneous polarization and piezoelectric polarization of the AlGaN barrier are obviously stronger than those of the GaN barrier, and due to the influence of quantum confinement stark effect (EQSE), the bending degree of valence band and conduction band of the InGaN/AlGaN quantum well is stronger, so that the separation degree of electron and hole pairs in space is more serious than that of an InGaN/GaN quantum well LED. Thus, the radiative recombination probability and the internal quantum efficiency are reduced, eventually leading to a reduction in luminous efficiency; on the other hand, due to the fact that the difference between the optimized growth temperatures of InGaN and AlGaN is large (InGaN needs to grow at a low temperature lower than 800 ℃ and AlGaN needs to grow at a high temperature higher than 900 ℃), quantum wells grown by using an InGaN/AlGaN structure have more defects, and the defects in the quantum wells are used as non-radiative recombination centers to enable the internal quantum efficiency of the near ultraviolet LED to be reduced rapidly. Designing a new quantum well structure and improving the material quality of the quantum well so as to improve the internal quantum efficiency of the near ultraviolet LED is a difficult problem to be solved urgently at present.

SUMMERY OF THE UTILITY MODEL

In order to overcome the above-mentioned shortcoming and not enough of prior art, the utility model aims to provide a LED epitaxial thin film with InGaN/GaN/AlGaN/GaN quantum well, this LED epitaxial thin film has advantages such as quantum well defect density is low, interior quantum efficiency height, but wide application in fields such as near ultraviolet, blue light, yellow green light LED.

The purpose of the utility model can be achieved by adopting one of the following technical schemes.

The LED epitaxial film with the InGaN/GaN/AlGaN/GaN quantum well comprises an n-GaN quantum well, an InGaN/GaN/AlGaN/GaN quantum well, an electron blocking layer and a p-GaN from bottom to top.

Furthermore, the number of cycles of the InGaN/GaN/AlGaN/GaN quantum wells is 1-10, the thickness of each cycle is 1-4 nm InGaN/1-3 nm GaN/3-10 nm AlGaN/1-3 nm GaN, wherein the InGaN well of the first quantum well starts with a 3-10 nm AlGaN/1-3 nm GaN barrier, and the InGaN well of the last quantum well ends with a 1-3 nm GaN/3-10 nm AlGaN barrier.

Furthermore, the growth temperature of an InGaN well of the InGaN/GaN/AlGaN/GaN quantum well is 700-900 ℃, the growth temperature of a GaN barrier is consistent with that of the InGaN well, and the growth temperature of the AlGaN barrier is 800-1000 ℃.

Furthermore, the In component of InGaN In the InGaN/GaN/AlGaN/GaN quantum well is 0.01-1, and the Al component of AlGaN is more than 0 and less than or equal to 1.

Further, the electron blocking layer is AlGaN or AlInGaN or a superlattice layer thereof.

Furthermore, the thickness of the electron blocking layer is 0-100 nm.

Further, the n-GaN is n-GaN prepared on a sapphire substrate, a Si substrate or a SiC substrate, and the thickness of the n-GaN is 1-5 mu m.

Furthermore, the thickness of the p-GaN is 50-500 nm, and the concentration of doped holes is 1.0 multiplied by 10¹⁷～1.0 ×10²⁰cm^-3。

The preparation method of the LED epitaxial film with the InGaN/GaN/AlGaN/GaN quantum well comprises the following steps:

1) preparing InGaN/GaN/AlGaN/GaN quantum wells with 1-10 periods on n-GaN by adopting MOCVD, wherein the InGaN layer of the first quantum well starts with a 3-10 nm AlGaN/1-3 nm GaN barrier, the InGaN layer of the last quantum well ends with a 1-3 nm GaN/3-10 nm AlGaN barrier, the growth temperature of the InGaN well is 700-900 ℃, the growth temperature of the GaN barrier is consistent with that of the InGaN well, the growth temperature of the AlGaN barrier is 800-1000 ℃, the In component of InGaN is 0.01-1, the Al component of AlGaN is 0-1, the pressure of a reaction chamber is 40-200Torr, and the rotation speed of a graphite plate is 800-1200 r/min;

2) preparing an AlGaN or AlInGaN electronic barrier layer on the quantum well obtained in the step 1), wherein the substrate temperature is 700-1200 ℃, the pressure of a reaction chamber is 40-200Torr, the rotation speed of a graphite disc is 800-1200r/min, the flow rate of trimethylaluminum (TMAl) is 0-500sccm, the flow rate of trimethylgallium (TMGa) is 0-500sccm, and NH is added₃The flow rate of (2) is 0-20 slm;

3) growing p-GaN on the electron blocking layer obtained in the step 2), wherein the substrate temperature is 700-1200 ℃, the pressure in the reaction chamber is 40-200Torr, the rotation speed of the graphite plate is 800-1200r/min, the flow of TMGa is 0-500sccm, and NH is added₃The flow of (2) is 0-20 slm, CP₂Mg flow rate of 50-300 sccm, and hole concentration of 1.0 × 10¹⁶-1.0×10²⁰cm^-3。

The LED epitaxial film with the InGaN/GaN/AlGaN/GaN quantum well is applied to the preparation of near ultraviolet, blue light and yellow green light LEDs.

Compared with the prior art, the beneficial effects of the utility model reside in that:

the utility model discloses a quantum well of InGaN/GaN/AlGaN/GaN structure. Wherein InGaN is a well layer, and GaN/AlGaN/GaN is a multiple barrier layer. On one hand, the structure keeps the strong limiting capacity of the AlGaN barrier on the current carrier, and the GaN is used as an insertion layer between the InGaN well and the AlGaN barrier, so that the polarization effect can be weakened, the quantum-limited Stark effect can be inhibited, the space separation degree of the current carrier can be reduced, and the internal quantum efficiency can be improved; on the other hand, the GaN barrier adopts the same growth temperature as the InGaN well and is used as a protective layer of the InGaN well, so that the adverse effect of high temperature on the InGaN well is isolated, the quality of the quantum well is improved, and the internal quantum efficiency of the LED is improved. The utility model discloses be favorable to preparing efficient near ultraviolet LED film, have characteristics such as quantum well defect density is low, interior quantum efficiency height, but wide application in near ultraviolet, blue light, yellow green light LED field.

Drawings

Fig. 1 is a schematic structural section view of the near-ultraviolet LED epitaxial film of the present invention.

Fig. 2 is a graph of simulated internal quantum efficiency of the near-uv LED of example 1.

Fig. 3 is an electroluminescence diagram of the near-ultraviolet LED epitaxial wafer prepared in example 1.

Detailed Description

The technical solution of the present invention will be described in further detail with reference to the following specific embodiments and accompanying drawings, but the embodiments and the scope of the present invention are not limited thereto.

In a specific embodiment, the structural cross-sectional view of the near ultraviolet LED epitaxial thin film with InGaN/GaN/AlGaN/GaN quantum well structure of the present invention is shown in fig. 1, and sequentially includes n-GaN 1, InGaN/GaN/AlGaN/GaN quantum well 2, electron blocking layer 3, and p-GaN 4 from bottom to top.

Wherein the thickness of the n-GaN 1 is 1-5 mu m; the period of the InGaN/GaN/AlGaN/GaN quantum well 2 is 1-10, the thickness of each period is 1-4 nm InGaN/1-3 nm GaN/3-10 nm AlGaN/1-3 nm GaN, wherein the InGaN layer of the first quantum well starts with a 3-10 nm AlGaN/1-3 nm GaN barrier, and the InGaN layer of the last quantum well ends with a 1-3 nm GaN/3-10 nm AlGaN barrier; the thickness of the electron blocking layer 3 is 0-100 nm; the thickness of the p-GaN is 50-200 nm.

Example 1

In is one_0.08Ga_0.92N/GaN/Al_0.15Ga_0.85The preparation method of the 395nm near ultraviolet LED epitaxial film with the N/GaN quantum well structure specifically comprises the following steps:

1) preparation of 9 cycles of In on n-GaN thin film on Si substrate by MOCVD_0.08Ga_0.92N/GaN/Al_0.15Ga_0.85N/GaN quantum well, In of the first quantum well_0.08Ga_0.92Before the N layer, a 10nm Al layer is coated_0.15Ga_0.85In of the last quantum well starting with N/2nm GaN barrier_0.08Ga_0.92After N layer, 2nm GaN/10nm Al_0.15Ga_0.85End of N barrier, In_0.08Ga_0.92The growth temperature of the N trap and the GaN barrier is 750 ℃, and the Al temperature is_0.15Ga_0.85The growth temperature of the N barrier is 950 ℃, the pressure of the reaction chamber is 50Torr, and the rotation speed of the graphite plate is 900 r/min.

2) Preparation of 30nm Al on quantum well by MOCVD_0.20Ga_0.80The temperature of the substrate is 1000 ℃, the pressure of the reaction chamber is 100Torr, the rotating speed of the graphite plate is 1200r/min, the flow rate of TMAl is 150sccm, the flow rate of TMGa is 200sccm, and NH is added₃At a flow rate of 5slm

3) Growing 200nm p-GaN on the electron barrier layer by MOCVD, wherein the substrate temperature is 900 ℃, the pressure in the reaction chamber is 200Torr, the rotation speed of the graphite plate is 1200r/min, the flow of TMGa is 350sccm, and NH is added₃Has a flow rate of 15slm, CP₂The flow rate of Mg was 250 sccm.

The LED epitaxial structure of the present embodiment is simulated by APSYS software, and the internal quantum efficiency is as shown in fig. 2, and under the injection current of 350mA, the internal quantum efficiency of the LED is 92%, which indicates that the ultraviolet LED of the structure has higher internal quantum efficiency; the electroluminescence spectrum of the LED epitaxial wafer prepared in this example is shown in fig. 3, and the emission wavelength of the ultraviolet LED is 395 nm.

Example 2

In is one_0.08Ga_0.92N/GaN/Al_0.15Ga_0.8539 of N/GaN quantum well structureThe preparation method of the 5nm near ultraviolet LED epitaxial film specifically comprises the following steps:

1) preparation of 1 cycle Al on n-GaN film on Si substrate by MOCVD_0.15Ga_0.85N/GaN/In_0.08Ga_0.92N/GaN/Al_0.15Ga_0.85N quantum well, In_0.08Ga_0.92The growth temperature of the N trap and the GaN barrier is 700 ℃, and the Al_0.15Ga_0.85The growth temperature of the N barrier is 1000 ℃, the pressure of the reaction chamber is 100Torr, and the rotation speed of the graphite plate is 1200 r/min.

2) Preparing and growing 200nm p-GaN on a quantum well by adopting MOCVD, wherein the substrate temperature is 900 ℃, the pressure of a reaction chamber is 200Torr, the rotating speed of a graphite plate is 1200r/min, the flow of TMGa is 350sccm, and NH is added₃Has a flow rate of 15slm, CP₂The flow rate of Mg was 250 sccm.

The LED epitaxial film on the Si substrate prepared in this example has very good crystal quality, and the test data is similar to that in example 1, and will not be described herein again.

Various other changes and modifications to the above-described embodiments and concepts may occur to those skilled in the art, and all such changes and modifications are intended to be included within the scope of the present invention as defined in the appended claims.

Claims

1. The LED epitaxial film with the InGaN/GaN/AlGaN/GaN quantum well is characterized by comprising an n-GaN (1), an InGaN/GaN/AlGaN/GaN quantum well (2), an electronic barrier layer (3) and a p-GaN (4) from bottom to top; the periodicity of the InGaN/GaN/AlGaN/GaN quantum well is 1-10; the thickness of each period in the InGaN/GaN/AlGaN/GaN quantum well is 1-4 nm of InGaN/1-3 nm of GaN/3-10 nm of AlGaN/1-3 nm of GaN, wherein the InGaN well of the first quantum well starts with a 3-10 nm AlGaN/1-3 nm GaN barrier, and the InGaN well of the last quantum well ends with a 1-3 nm GaN/3-10 nm AlGaN barrier.

2. The LED epitaxial film with InGaN/GaN/AlGaN/GaN quantum wells of claim 1, wherein the electron blocking layer is AlGaN or AlInGaN.

3. The LED epitaxial film with InGaN/GaN/AlGaN/GaN quantum wells according to claim 1, wherein the thickness of the electron blocking layer is 0-100 nm.

4. The LED epitaxial film with InGaN/GaN/AlGaN/GaN quantum wells of claim 1, wherein the n-GaN is n-GaN fabricated on sapphire, Si or SiC substrates.

5. The LED epitaxial film with InGaN/GaN/AlGaN/GaN quantum wells according to claim 1, wherein the n-GaN has a thickness of 1-5 μm.

6. The LED epitaxial film with InGaN/GaN/AlGaN/GaN quantum wells according to claim 1, wherein the p-GaN has a thickness of 50-500 nm.