WO2018076407A1

WO2018076407A1 - Nonpolar nanorod led grown on lithium gallate substrate and preparation method therefor

Info

Publication number: WO2018076407A1
Application number: PCT/CN2016/105813
Authority: WO
Inventors: 李国强; 王文樑; 杨美娟
Original assignee: 华南理工大学
Priority date: 2016-10-31
Filing date: 2016-11-15
Publication date: 2018-05-03
Also published as: CN106374023B; CN106374023A

Abstract

Disclosed are a nanorod LED grown on a lithium gallate substrate and a preparation method therefor. The nonpolar nanorod LED grown on the lithium gallate substrate comprises an LiGaO₂ substrate (10), a GaN nanorod array (11) grown on the LiGaO₂ substrate, a non-doped GaN layer (13) grown on the GaN nanorod array, an n-type doped GaN layer (14) grown on the non-doped GaN layer, an InGaN/GaN quantum well (15) grown on the n-type doped GaN layer, and a p-type doped GaN layer (16) grown on the InGaN/GaN quantum well, wherein the GaN nanorod array is a nonpolar GaN nanorod array. The selected lithium gallate substrate is low in material cost; the prepared nanorod array is controllable in dimensions and uniform in orientation; and the resulting nonpolar nanorod LED has a low defect density, and excellent electrical and optical properties.

Description

Non-polar nano column LED grown on lithium gallate substrate and preparation method thereof

Technical field

The invention relates to the field of nano-array LED growth and preparation, in particular to a nano-column LED grown on a lithium gallate (LiGaO ₂ ) substrate and a preparation method thereof.

Background technique

GaN and its related Group III nitrides have excellent electrical, optical and acoustic properties and have been widely used in the fabrication of light-emitting diodes (LEDs), laser diodes (LDs) and field effect transistors. In recent years, GaN-based nano-column LEDs have attracted much attention as a potential LED structure, because the nano-column LEDs have a high aspect ratio (area/volume) compared to planar LEDs, which can significantly reduce wear. Dislocation density; secondly, the nano-column LED can greatly improve the light-emitting efficiency of the LED and realize the coupling and exit of the light; finally, by controlling the size of the nano-column LED, the wavelength of the nano-column LED can be changed to prepare a single-chip multi-color illumination. The nano-pillar LEDs have opened up new avenues for the preparation of low-cost white LEDs.

At present, most of GaN-based nano-column LEDs are constructed based on their polar faces. The quantum bound Stark effect (QCSE) of the polar surface causes the LED band to bend and tilt, which causes the separation of electrons and holes, which is seriously reduced. The radiation recombination efficiency of the carriers causes the LED emission wavelength to be unstable. The non-polar surface epitaxial GaN-based LED can suppress the wavelength shift caused by the bending and tilting of the energy band, overcome the separation of electrons and holes caused by the QCSE effect, and theoretically improve the luminous efficiency of the LED by nearly double. At the same time, the non-polar InGaN/GaN quantum well structure has been proven to have a special polarization characteristic, which can be used in screen display devices to remove the polarization filter, thereby reducing the loss caused by the polarization filter and improving the light uniformity of the screen. To achieve energy saving and improve the color tone.

The non-polar plane GaN is more likely to form defects during growth than the polar plane GaN. Therefore, the selection of non-polar GaN epitaxial substrates is particularly important. At present, commercial LEDs are mainly epitaxially grown on sapphire substrates. However, the lattice mismatch between sapphire and GaN is high, resulting in the formation of GaN nanopillars. The high dislocation density, which reduces the carrier mobility of the material, ultimately affects device performance. The lattice mismatch of LiGaO ₂ substrate and non-polar GaN in the b and c directions is 0.1% and 4.0%, respectively, and the thermal expansion coefficient is very close (the thermal expansion coefficient of LiGaO2 substrate is 4.0×10 ^-6 K ^{-1 , respectively).} Compared with 3.8×10 ^-6 K ^-1 , GaN has thermal expansion coefficients of 5.59×10 ^-6 K ^-1 and 3.17×10 ^-6 K ^-1 , respectively, which is one of the best substrates for epitaxial non-polar plane GaN. However, the chemical nature of the high temperature instability LiGaO ₂ substrate, a LiGaO ₂ substrate to make GaN-based nano-column LED is possible to realize large-scale applications, it is necessary to find a new method of growing a GaN-based nano-column LED on the substrate and process LiGaO ₂ .

Summary of the invention

In order to overcome the above disadvantages and disadvantages of the prior art, the object of the present invention is to provide a nano-pillar LED grown on a lithium gallate substrate and a preparation method thereof, wherein the selected lithium gallate substrate material has low cost and is prepared. The nano-pillar array is controllable in size and uniform in orientation, and the obtained non-polar nano-pillar LED has low defect density and excellent electrical and optical properties.

The object of the invention is achieved by the following technical solutions:

Non-polar nanocolumn LEDs grown on a lithium gallate substrate, including LiGaO ₂ substrates, GaN nanopillar arrays grown on LiGaO ₂ substrates, undoped GaN layers grown on GaN nanopillar arrays, grown An n-doped GaN layer on the undoped GaN layer, an InGaN/GaN quantum well grown on the n-doped GaN layer, and a p-doped GaN layer grown on the InGaN/GaN quantum well. The GaN nanopillar array is a non-polar GaN nanopillar array.

The non-polar nano-pillar LED grown on the lithium gallate substrate further includes an isolation layer deposited on the sidewalls of the GaN nano-pillar array and the LiGaO ₂ substrate not covered by the nano-pillar array. The isolation layer is a SiN _x , SiO ₂ or Al ₂ O ₃ isolation layer. SiN _x , x is 1 to 2.

The LiGaO ₂ substrate has an epitaxial plane of 0.2 to 1° in a (100) plane (110) direction.

The GaN nanopillar array was prepared from a non-polar GaN buffer layer grown on a LiGaO ₂ substrate.

The non-polar GaN buffer layer is a non-polar plane GaN, and the crystal epitaxial orientation relationship is such that the (1-100) plane of GaN is parallel to the (100) plane of LiGaO ₂ . That is, the GaN nano-pillar array is a non-polar plane GaN, and the crystal epitaxial orientation relationship is such that the (1-100) plane of GaN is parallel to the (100) plane of LiGaO ₂ .

The non-polar GaN buffer layer is formed by epitaxial growth on a LiGaO ₂ substrate at a low temperature by using a PLD technology, which can effectively alleviate the high-temperature growth of Li atoms in the LiGaO ₂ substrate and interact with the non-polar GaN buffer layer. A serious interface reaction occurs between them.

The GaN nano-pillar array is prepared by using TracePro software to optimize nano-column arrangement, and is prepared by using nano-imprint technology and etching on a non-polar GaN buffer layer, and the obtained nano-pillar array is uniform in size. The GaN nano-pillar array grown on the LiGaO ₂ substrate was transferred to a metal organic compound vapor deposition reaction chamber (MOCVD) for the preparation of nano-column LEDs by selective growth.

The GaN nano-pillar array has a height of 500 to 1000 nm, a pitch of 150 to 250 nm, and a diameter of 100 to 200 nm.

The undoped GaN layer has a thickness of 200 to 300 nm; and the n-type doped GaN layer has a doping concentration of 3×10 ¹⁸ to 9×10 ¹⁸ cm ⁻³ and a thickness of 2 to 4 μm.

The InGaN/GaN quantum well is an InGaN well layer/GaN barrier layer of 8 to 13 cycles, wherein the thickness of the InGaN well layer is 3 to 5 nm, and the thickness of the GaN barrier layer is 10 to 15 nm.

The p-type doped GaN layer has a doping concentration of 3×10 ¹⁷ to 9×10 ¹⁷ cm ⁻³ and a thickness of 300 to 350 nm.

The thickness of the isolation layer is 10 to 50 nm;

The method for preparing the non-polar nano-pillar LED grown on a lithium gallate substrate comprises the following steps:

(1) Selection of substrate and crystal orientation: LiGaO ₂ substrate is used, and the epitaxial plane is 0.2 to 1° in the (100) plane (110) direction. The crystal epitaxial orientation relationship is: (1-100) plane of GaN. Parallel to the (100) plane of LiGaO ₂ ;

(2) polishing, cleaning and annealing treatment of the substrate surface, the specific process of the annealing is: placing the substrate into the annealing chamber, and annealing the LiGaO ₂ substrate in an air atmosphere at 800 to 900 ° C for 3 to 4 hours. Then air cooled to room temperature;

(3) Non-polar GaN buffer layer epitaxial growth: PLD technology, substrate temperature is 150-250 ° C, nitrogen plasma flow rate is 3 ~ 4.5sccm, RF activation power is 400 ~ 450W, non-polar growth a GaN buffer layer having a buffer layer thickness of 500 to 1000 nm; and a crystal epitaxial orientation relationship: a (1-100) plane of GaN is parallel to a (100) plane of LiGaO ₂ ; and the substrate rotation speed is 10 r/min in the PLD technique. The target distance is 5 cm, the laser wavelength is 248 nm, the laser energy is 250 mJ/p, and the frequency is 20 Hz; the Ga source is a GaN target, and the purity thereof is 99.99%;

(4) Preparation of GaN nano-pillar array: The nano-column arrangement was optimized by using TracePro software, and the non-polar GaN buffer layer on the LiGaO ₂ substrate was etched down by nanoimprint technology and dry etching process. a GaN nano-pillar array having a height of 500 to 1000 nm, a diameter of 100 to 200 nm, and a pitch of 150 to 250 nm; the height of the GaN nano-pillar array is the same as the height of the non-polar GaN buffer layer;

(5) deposition of an isolation layer: depositing an isolation layer on a sidewall of the nano-pillar in the GaN nano-pillar array and a substrate not covered by the nano-pillar array by chemical vapor deposition, atomic layer deposition or magnetron sputtering techniques, The material of the isolation layer is SiN _x , SiO ₂ or Al ₂ O ₃ , and has a thickness of 10 to 50 nm;

(6) Epitaxial growth of undoped GaN layer: in MOCVD, the reaction chamber temperature is 1000-1300 ° C, the pressure in the reaction chamber is 150-200 Torr, and the undoped GaN layer is grown on the GaN nano-pillar array to a thickness of 200 ~300nm;

(7) Epitaxial growth of the n-type doped GaN layer: raising the temperature of the reaction chamber to 1000 to 1500 ° C, and growing on the undoped GaN layer obtained in the step (6) under the condition that the reaction chamber pressure is 150 to 200 Torr. a doped GaN layer having a doping concentration of 3×10 ¹⁸ to 9×10 ¹⁸ cm ⁻³ and a thickness of 2 to 4 μm;

(8) Epitaxial growth of InGaN/GaN multiple quantum wells: the temperature of the reaction chamber is lowered to 700-780 ° C, and ammonia, nitrogen, trimethylgallium and trimethyl groups are introduced under the pressure of 150 to 200 Torr in the reaction chamber. Indium, an InGaN/GaN multiple quantum well is grown on the n-type doped GaN layer obtained in the step (7), and the InGaN/GaN quantum well is an 8 to 13-cycle InGaN well layer/GaN barrier layer, wherein the thickness of the InGaN well layer 3 to 5 nm, the thickness of the GaN barrier layer is 10 to 15 nm;

(9) Epitaxial growth of p-type doped GaN layer: the temperature of the reaction chamber is raised to 900 to 1100 ° C, and the pressure of the reaction chamber is 150 to 200 Torr, and magnesium pentoxide, ammonia gas, nitrogen gas, trimethyl group are introduced. Gallium, a p-type doped GaN layer is grown on the InGaN/GaN multiple quantum well obtained in the step (8) at a doping concentration of 3 × 10 ¹⁷ to 9 × 10 ¹⁷ cm ^-3 and a thickness of 300 to 350 nm.

In step (6), the Ga source is TMGa in the epitaxial growth of the undoped GaN layer; the nitrogen source is NH ₃ ; the flow rate of the Ga source is 350-450 sccm, and the flow rate of the nitrogen source is 50-65 slm;

The doping source doped in the epitaxial growth of the n-type doped GaN layer in step (7) is silane; the Ga source is TMGa; the nitrogen source is NH ₃ ; the flow rate of each source is: Ga source 350-450 sccm, nitrogen source 50 ~ 65slm, doping source 100 ~ 200sccm;

The flow rate of the ammonia gas in the step (8) is 25 to 35 slm, the flow rate of nitrogen gas is 25 to 35 slm, the flow rate of trimethyl gallium is 100 to 150 sccm, and the flow rate of trimethyl indium is 450 to 550 sccm;

The flow rate of the trimethylgallium in the step (9) is 350 to 450 sccm, the flow rate of the ammonia gas is 50 to 65 slm, the flow rate of the nitrogen gas is 50 to 65 slm, and the flow rate of the magnesium pentoxide is 150 to 250 sccm.

Step (1) polishing the surface of the substrate, specifically: first polishing the surface of the LiGaO ₂ substrate with a diamond slurry, and observing the surface of the substrate with an optical microscope until there is no scratch, and then polishing by chemical mechanical polishing. deal with.

The cleaning is specifically: the LiGaO ₂ substrate is ultrasonically cleaned in deionized water at room temperature for 3 to 5 minutes, the surface of the LiGaO ₂ substrate is removed, and then the surface organic matter is removed by washing with hydrochloric acid, acetone and ethanol. Dry with dry nitrogen.

Compared with the prior art, the present invention has the following advantages and benefits:

(1) The present invention uses LiGaO ₂ as a substrate, and a LiGaO ₂ substrate is easily obtained, which is inexpensive, and is advantageous in reducing production cost.

(2) The present invention adopts nanoimprint technology and etching to obtain a high-quality nano-pillar array, and then transfers the nano-pillar array grown on the substrate to MOCVD to perform nano-column LED epitaxial material preparation by selective growth; The difficulty of LED growth eliminates the adverse effects of introducing impurities by using a catalyst, and is advantageous for obtaining high-quality nano-pillar LEDs with controllable size and uniform orientation.

(3) The present invention fully utilizes the respective advantages of PLD and MOCVD: firstly, a low-level (150-250 ° C) epitaxial growth of a layer of GaN or a buffer layer on a LiGaO ₂ substrate is performed using a PLD technique, and the interface reaction is successfully suppressed. One-step preparation of high-quality low-defect nano-pillar arrays is paved; then transferred to high-temperature epitaxial u-GaN, n-GaN, P-GaN, and quantum wells in MOCVD, giving full play to the advantages of MOCVD, increasing growth rate and productivity ;

(4) The present invention uses LiGaO ₂ (100) having a lattice mismatch with GaN and a low thermal mismatch as a substrate for growing non-polar nano-pillar LEDs, which can not only effectively reduce thermal stress and reduce formation of dislocations, but also Effectively eliminate the influence of the quantum bound Stark effect; the prepared high-quality non-polar nano-column LED epitaxial material can greatly improve the luminous efficiency of nitride devices such as semiconductor lasers, light-emitting diodes and solar cells.

DRAWINGS

1 is a front elevational view of a nanopillar LED grown on a lithium gallate (LiGaO ₂ ) substrate of the present invention;

2 is an XRD diffraction pattern of a non-polar GaN buffer layer prepared in Example 1;

3 is a schematic cross-sectional view of a GaN nano-pillar array prepared in Example 1;

4 is a plan view of a nano-pillar LED grown on a lithium gallate (LiGaO ₂ ) substrate of Example 1.

detailed description

The present invention will be further described in detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

A front view of a nanopillar LED grown on a lithium gallate (LiGaO ₂ ) substrate of the present invention is shown in FIG. 1 and includes a LiGaO ₂ substrate 10 grown on a LiGaO ₂ substrate 10 on a GaN nanopillar array 11 The GaN nano-pillar array is prepared by nanoimprinting and etching of a non-polar GaN buffer layer grown on a LiGaO ₂ substrate, deposited on the sidewalls of the GaN nano-pillar array 11 and not covered by the nano-pillar array. The isolation layer 12 on the LiGaO ₂ substrate 10, the undoped GaN layer 13 grown on the GaN nano-pillar array 11, the n-doped GaN layer 14 grown on the undoped GaN layer 13, and grown in the n-type The InGaN/GaN quantum well 15 on the GaN layer 14 is doped, and the p-doped GaN layer 16 is grown on the InGaN/GaN quantum well 15.

The LiGaO ₂ substrate has an epitaxial plane of 0.2 to 1° in a (100) plane (110) direction. The GaN nano-pillar array is a non-polar plane GaN, and the crystal epitaxial orientation relationship is such that the (1-100) plane of GaN is parallel to the (100) plane of LiGaO ₂ .

The GaN nano-pillar array has a height of 500 to 1000 nm, a pitch of 150 to 250 nm, and a diameter of 100 to 200 nm. The undoped GaN layer has a thickness of 200 to 300 nm; the n-type doped GaN layer has a thickness of 2 to 4 μm; and the InGaN/GaN quantum well has an 8 to 13 period of InGaN well layer/GaN barrier layer. Wherein the thickness of the InGaN well layer is 3 to 5 nm, and the thickness of the GaN barrier layer is 10 to 15 nm;

The p-doped GaN layer has a thickness of 300 to 350 nm. The separator has a thickness of 10 to 50 nm.

Example 1

The method for preparing the nano-pillar LED grown on the lithium gallate substrate of the embodiment comprises the following steps:

(1) Substrate and its crystal orientation: a LiGaO ₂ substrate is used, and the (100) plane (110) direction is 0.6° as an epitaxial plane;

(2) substrate surface polishing, cleaning and annealing treatment, the specific process of the annealing is: placing the substrate into the annealing chamber, annealing the LiGaO ₂ substrate in an air atmosphere at 880 ° C for 3 hours and then air cooling to room temperature ;

The surface of the substrate is polished, specifically: first, the surface of the LiGaO ₂ substrate is polished with a diamond slurry, and the surface of the substrate is observed with an optical microscope until there is no scratch, and then polished by chemical mechanical polishing;

The cleaning is specifically: the LiGaO ₂ substrate is ultrasonically cleaned in deionized water at room temperature for 3 minutes to remove the sticky particles on the surface of the LiGaO ₂ substrate, and then washed successively with hydrochloric acid, acetone, ethanol to remove surface organic matter, and dried. Blow dry with nitrogen;

(3) Non-polar buffer layer epitaxial growth: using PLD technology, substrate temperature is 200 ° C, substrate rotation speed is 10 r / min, target base distance is 5 cm, laser wavelength is 248 nm, laser energy is 250 mJ / p, frequency is 20 Hz The nitrogen plasma flow rate is 4 sccm, the RF activation power is 420 W, and the non-polar GaN buffer layer is grown to a thickness of 500 nm; the crystal epitaxial orientation relationship is: (1-100) plane of GaN is parallel to LiGaO ₂ (100) Surface; Ga source is a GaN target with a purity of 99.99%;

(4) Preparation of nano-pillar array: By using TracePro software to optimize nano-column arrangement, nano-imprint technology and dry etching process are used to etch the non-polar GaN buffer layer on LiGaO ₂ substrate to obtain GaN. Nanocolumn array, the height of the nanocolumn is 500 nm, the diameter is 200 nm, and the adjacent spacing is 250 nm;

(5) Deposition of an isolation layer: a spacer layer is deposited on a sidewall of a nanocolumn and a substrate not covered by a nanocolumn in a GaN nanocolumn array by chemical vapor deposition, atomic layer deposition or magnetron sputtering, the nanometer The material of the pillar sidewall isolation layer is SiN _x and has a thickness of 10 nm;

(6) Epitaxial growth of undoped GaN layer: in MOCVD, the reaction chamber temperature is 1200 ° C, the pressure in the reaction chamber is 150 Torr, the undoped GaN layer is grown on the GaN nano-pillar array, and the thickness is 200 nm; the Ga source is TMGa The nitrogen source is NH ₃ ; the gas flow rate of each source is Ga source 380 sccm, nitrogen source 56 slm;

(7) Epitaxial growth of an n-type doped GaN layer: the reaction chamber temperature was raised to 1200 ° C, and n-type doped GaN was grown on the undoped GaN layer obtained in the step (6) under a reaction chamber pressure of 150 Torr. The layer has a doping concentration of 3×10 ¹⁸ cm ^-3 and a thickness of 2 μm; the doping source is silane; the Ga source is TMGa; the nitrogen source is NH ₃ ; the gas flow rate of each source is: Ga source 380 sccm, nitrogen source 56 slm, Doping source 125sccm;

(8) Epitaxial growth of InGaN/GaN multiple quantum wells: the temperature of the reaction chamber is lowered to 720 ° C, and ammonia, nitrogen, trimethyl gallium and trimethyl indium are introduced in the reaction chamber at a pressure of 150 Torr. (7) The InGaN/GaN multiple quantum well is grown on the obtained n-type doped GaN layer, and the InGaN/GaN quantum well is an 8-cell InGaN well layer/GaN barrier layer, wherein the thickness of the InGaN well layer is 3 nm, and the GaN barrier layer The thickness of each source is 10 nm; the flow rate of each source is: 475 sccm of indium source, 140 sccm of gallium source, 27 slm of nitrogen source;

(9) Epitaxial growth of p-type doped GaN layer: the temperature of the reaction chamber is raised to 900 to 1100 ° C, and the pressure of the reaction chamber is 150 Torr, and ferrocene, ammonia, nitrogen, and trimethylgallium are introduced. The flow rate is 380 sccm, the flow rate of ammonia gas and nitrogen gas is 56 slm, and the flow rate of magnesium pentoxide is 200 sccm. The p-type doped GaN layer is grown on the InGaN/GaN multiple quantum well obtained in the step (8), and the doping concentration is 3×10. ¹⁷ cm ^-3 , thickness 300 nm.

The XRD diffraction pattern of the non-polar GaN buffer layer prepared in Example 1 is shown in FIG. 2; as can be seen from FIG. 2, the non-polar buffer layer grown on the lithium gallate substrate prepared in this embodiment: GaN is the m-plane The diffraction angle of XRD is 2θ=32.31°, that is, GaN of a non-polar plane.

A schematic cross-sectional view of a GaN nano-array etched on a non-polar GaN buffer layer in this embodiment is shown in FIG.

A top view of the nano-pillar LED grown on the lithium gallate substrate prepared in this embodiment is shown in FIG.

Example 2

(1) Selection of the substrate and its crystal orientation: a LiGaO ₂ substrate is used, and the epitaxial surface is 0.5° in the (100) plane (110) direction;

(2) substrate surface polishing, cleaning and annealing treatment, the specific process of the annealing is: placing the substrate into the annealing chamber, annealing the LiGaO ₂ substrate in an air atmosphere at 800-900 ° C for 4 hours and then air cooling To room temperature;

(3) Non-polar buffer layer epitaxial growth: using PLD technology, the substrate temperature is adjusted to 150-250 ° C, the substrate rotation speed is 10 r / min, the target base distance is 5 cm, the laser wavelength is 248 nm, and the laser energy is 250 mJ / p The frequency of 20 Hz, the plasma flow rate of nitrogen is 3 to 4.5 sccm, the RF activation power is 400-450 W, and the non-polar GaN buffer layer is grown, the buffer layer thickness is 1000 nm; the crystal epitaxial orientation relationship is: GaN (1- 100) face parallel to the (100) plane of LiGaO ₂ ; Ga source is a GaN target, the purity of which is 99.99%;

(4) Preparation of nano-pillar array: By using TracePro software to optimize nano-column arrangement, nano-imprint technology and dry etching process are used to etch the non-polar GaN buffer layer on LiGaO ₂ substrate to obtain GaN. a nanocolumn array having a height of 1000 nm, a diameter of 100 nm, and a pitch of 150 nm;

(5) Deposition of the isolation layer: a spacer layer is deposited on the sidewall of the GaN nano-pillar array and the substrate not covered by the nano-pillar by chemical vapor deposition, atomic layer deposition or magnetron sputtering, the material of the isolation layer Is SiO ₂ and has a thickness of 50 nm;

(6) Epitaxial growth of undoped GaN layer: in MOCVD, the reaction chamber temperature is 1100 ° C, the reaction chamber pressure is 200 Torr, and the undoped GaN layer is grown on the GaN nano-pillar array to a thickness of 300 nm; TMGa; nitrogen source is NH ₃ ; gas flow rate of each source is Ga source 380sccm, nitrogen source 56slm;

(7) Epitaxial growth of the n-type doped GaN layer: the reaction chamber temperature was raised to 1500 ° C, and n-type doped GaN was grown on the undoped GaN layer obtained in the step (6) under a reaction chamber pressure of 200 Torr. The layer has a doping concentration of 9×10 ¹⁸ cm ^-3 and a thickness of 4 μm; the doping source is silane; the Ga source is TMGa; the nitrogen source is NH ₃ ; the gas flow rate of each source is Ga source 380 sccm, nitrogen source 56 slm, and doping Miscellaneous source 125sccm;

(8) Epitaxial growth of InGaN/GaN multiple quantum wells: the temperature of the reaction chamber is lowered to 750 ° C, and ammonia, nitrogen, trimethyl gallium and trimethyl indium are introduced in the reaction chamber at a pressure of 200 Torr. (7) The InGaN/GaN multiple quantum well is grown on the obtained n-type doped GaN layer, and the InGaN/GaN quantum well is a 13-cycle InGaN well layer/GaN barrier layer, wherein the thickness of the InGaN well layer is 5 nm, and the GaN barrier layer The thickness of the anode is 15 nm; the flow rate of the indium source is 475 sccm, the flow rate of the gallium source is 140 sccm, and the flow rate of the nitrogen source is 27 slm;

(9) Epitaxial growth of p-type doped GaN layer: the temperature of the reaction chamber is raised to 1000 ° C, and the pressure of the reaction chamber is 150 Torr, and magnesium pentoxide, ammonia gas, nitrogen gas and trimethyl gallium are introduced in the step. (8) The p-doped GaN layer grown on the obtained InGaN/GaN multiple quantum well has a doping concentration of 9×10 ¹⁷ cm ^-3 and a thickness of 350 nm; the gas flow rate of each source is: Ga source 380 sccm, nitrogen source 56 slm The doping source is 200 sccm.

The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and combinations thereof may be made without departing from the spirit and scope of the invention. Simplifications should all be equivalent replacements and are included in the scope of the present invention.

Claims

A non-polar nano-pillar LED grown on a lithium gallate substrate, comprising: a LiGaO 2 substrate, a GaN nano-pillar array grown on a LiGaO 2 substrate, and an undoped layer grown on a GaN nano-pillar array GaN layer, n-doped GaN layer grown on undoped GaN layer, InGaN/GaN quantum well grown on n-doped GaN layer, p-doped GaN layer grown on InGaN/GaN quantum well The GaN nano-pillar array is a non-polar GaN nano-pillar array.
The non-polar nano-pillar LED grown on a lithium gallate substrate according to claim 1, wherein the LiGaO 2 substrate has an epitaxial plane of 0.2 to 1° in a (100) plane (110) direction.
The non-polar nano-pillar LED grown on a lithium gallate substrate according to claim 1, wherein the GaN nano-pillar array is prepared from a non-polar GaN buffer layer grown on a LiGaO 2 substrate. The non-polar GaN buffer layer is a non-polar plane GaN, and the crystal epitaxial orientation relationship is: a (1-100) plane of GaN parallel to a (100) plane of LiGaO 2 ;

The GaN nano-pillar array is a non-polar plane GaN, and the crystal epitaxial orientation relationship is such that the (1-100) plane of GaN is parallel to the (100) plane of LiGaO 2 .
The non-polar nano-pillar LED grown on a lithium gallate substrate according to claim 1, wherein the GaN nano-pillar array has a height of 500 to 1000 nm, a pitch of 150 to 250 nm, and a diameter of 100 to 200 nm. .
The non-polar nano-pillar LED grown on a lithium gallate substrate according to claim 1, wherein the undoped GaN layer has a thickness of 200 to 300 nm; and the thickness of the n-type doped GaN layer 2 to 4 μm;

The InGaN/GaN quantum well is an InGaN well layer/GaN barrier layer of 8 to 13 cycles, wherein the thickness of the InGaN well layer is 3 to 5 nm, and the thickness of the GaN barrier layer is 10 to 15 nm;

The p-doped GaN layer has a thickness of 300 to 350 nm.
The non-polar nano-pillar LED grown on a lithium gallate substrate according to claim 1, wherein the n-type doped GaN layer has a doping concentration of 3×10 18 to 9×10 18 cm − 3 ; The p-doped GaN layer has a doping concentration of 3 × 10 17 to 9 × 10 17 cm -3 .
The non-polar nano-pillar LED grown on a lithium gallate substrate according to claim 1, wherein the non-polar nano-pillar LED grown on the lithium gallate substrate further comprises an isolation layer, The spacer layer is deposited on the sidewalls of the GaN nanopillar array and the LiGaO 2 substrate not covered by the nanopillar array.
The non-polar nano-pillar LED grown on a lithium gallate substrate according to claim 7, wherein the material of the isolation layer is SiN x , SiO 2 or Al 2 O 3 ; the thickness of the isolation layer It is 10 to 50 nm.
The method for preparing a non-polar nano-pillar LED grown on a lithium gallate substrate according to any one of claims 1 to 8, comprising the steps of:

(1) Selection of substrate and crystal orientation: LiGaO 2 substrate is used, and the epitaxial plane is 0.2 to 1° in the (100) plane (110) direction. The crystal epitaxial orientation relationship is: (1-100) plane of GaN. Parallel to the (100) plane of LiGaO 2 ;

(2) polishing, cleaning and annealing treatment of the substrate surface, the specific process of the annealing is: placing the substrate into the annealing chamber, and annealing the LiGaO 2 substrate in an air atmosphere at 800 to 900 ° C for 3 to 4 hours. Then air cooled to room temperature;

(3) Non-polar GaN buffer layer epitaxial growth: PLD technology, substrate temperature is 150-250 ° C, nitrogen plasma flow rate is 3 ~ 4.5sccm, RF activation power is 400 ~ 450W, non-polar growth GaN buffer layer, buffer layer thickness is 500-1000 nm; crystal epitaxial orientation relationship is: (1-100) plane of GaN is parallel to (100) plane of LiGaO 2 ; the substrate rotation speed is 10r/min in PLD technology, The target base distance is 5 cm, the laser wavelength is 248 nm, the laser energy is 250 mJ/p, and the frequency is 20 Hz; the Ga source is a GaN target;

(4) Preparation of GaN nano-pillar array: The nano-column arrangement was optimized by using TracePro software, and the non-polar GaN buffer layer on the LiGaO 2 substrate was etched down by nanoimprint technology and dry etching process. a GaN nano-pillar array having a height of 500 to 1000 nm, a diameter of 100 to 200 nm, and a pitch of 150 to 250 nm; the height of the GaN nano-pillar array is the same as the height of the non-polar GaN buffer layer;

(5) deposition of an isolation layer: depositing an isolation layer on a sidewall of the nano-pillar in the GaN nano-pillar array and a substrate not covered by the nano-pillar array by chemical vapor deposition, atomic layer deposition or magnetron sputtering techniques, The material of the isolation layer is SiN x , SiO 2 or Al 2 O 3 , and has a thickness of 10 to 50 nm;

(6) Epitaxial growth of undoped GaN layer: in MOCVD, the reaction chamber temperature is 1000-1300 ° C, the pressure in the reaction chamber is 150-200 Torr, and the undoped GaN layer is grown on the GaN nano-pillar array to a thickness of 200 ~300nm;

(7) Epitaxial growth of the n-type doped GaN layer: raising the temperature of the reaction chamber to 1000 to 1500 ° C, and growing on the undoped GaN layer obtained in the step (6) under the condition that the reaction chamber pressure is 150 to 200 Torr. a doped GaN layer having a doping concentration of 3×10 18 to 9×10 18 cm −3 and a thickness of 2 to 4 μm;

(8) Epitaxial growth of InGaN/GaN multiple quantum wells: the temperature of the reaction chamber is lowered to 700-780 ° C, and ammonia, nitrogen, trimethylgallium and trimethyl groups are introduced under the pressure of 150 to 200 Torr in the reaction chamber. Indium, an InGaN/GaN multiple quantum well is grown on the n-type doped GaN layer obtained in the step (7), and the InGaN/GaN quantum well is an 8 to 13-cycle InGaN well layer/GaN barrier layer, wherein the thickness of the InGaN well layer 3 to 5 nm, the thickness of the GaN barrier layer is 10 to 15 nm;

(9) Epitaxial growth of p-type doped GaN layer: the temperature of the reaction chamber is raised to 900-1100 ° C, and the pressure of the reaction chamber is 150-200 Torr, and magnesium pentoxide, ammonia gas, nitrogen gas and trimethyl group are introduced. Gallium, a p-type doped GaN layer is grown on the InGaN/GaN multiple quantum well obtained in the step (8) at a doping concentration of 3 × 10 17 to 9 × 10 17 cm -3 and a thickness of 300 to 350 nm.
The method for preparing a non-polar nano-pillar LED grown on a lithium gallate substrate according to claim 9, wherein the Ga source is TMGa in the epitaxial growth of the undoped GaN layer in the step (6); The source is NH 3 ; the flow rate of the Ga source is 350-450 sccm, and the flow rate of the nitrogen source is 50-65 slm;

The doping source doped in the epitaxial growth of the n-type doped GaN layer in step (7) is silane; the Ga source is TMGa; the nitrogen source is NH 3 ; the flow rate of each source is: Ga source 350-450 sccm, nitrogen source 50 ~ 65slm, doping source 100 ~ 200sccm;

The flow rate of the ammonia gas in the step (8) is 25 to 35 slm, the flow rate of nitrogen gas is 25 to 35 slm, the flow rate of trimethyl gallium is 100 to 150 sccm, and the flow rate of trimethyl indium is 450 to 550 sccm;

The flow rate of the trimethylgallium in the step (9) is 350 to 450 sccm, the flow rate of the ammonia gas is 50 to 65 slm, the flow rate of the nitrogen gas is 50 to 65 slm, and the flow rate of the magnesium pentoxide is 150 to 250 sccm.