阅读说明：本技术 阻碍半极性面氮化镓生长并制备自剥离氮化镓晶体的方法 (Method for hindering growth of semipolar plane gallium nitride and preparing self-stripping gallium nitride crystal ) 是由 邵永亮 张保国 胡海啸 郝霄鹏 吴拥中 吕洪 于 2021-06-24 设计创作，主要内容包括：本发明公开了一种阻碍半极性面氮化镓生长并制备自剥离氮化镓晶体的方法,包括以下步骤：制备具有倒六棱锥结构、暴露出半极性面的GaN晶体；可还原的金属盐溶液或金属盐熔液在GaN非极性面电解还原得到对应金属；以及在GaN晶体生长过程中,电沉积金属阻碍非极性面GaN生长,产生空隙进而在降温过程中由于应力作用得到自剥离GaN晶体。通过在半极性面沉积金属的方法,仅在样品半极性面形成了阻碍结构,借助空位辅助分离原理,制备的处理衬底在后期生长GaN体单晶过程中,有助于缓解晶体中的应力和实现晶体的自剥离。(The invention discloses a method for hindering the growth of semipolar plane gallium nitride and preparing self-stripping gallium nitride crystal, which comprises the following steps: preparing a GaN crystal with an inverted hexagonal pyramid structure and exposed semi-polar surfaces; the reducible metal salt solution or metal salt solution is electrolyzed and reduced on the GaN nonpolar surface to obtain corresponding metal; and in the growth process of the GaN crystal, the electro-deposition metal hinders the growth of the GaN on the nonpolar surface, and a gap is generated, so that the self-stripping GaN crystal is obtained due to the stress effect in the cooling process. By the method of depositing metal on the semipolar surface, an obstruction structure is formed only on the semipolar surface of a sample, and by means of the vacancy auxiliary separation principle, the prepared processing substrate is beneficial to relieving the stress in the crystal and realizing the self-peeling of the crystal in the later growth process of the GaN bulk single crystal.)

1. A method for hindering the growth of semipolar plane gallium nitride and preparing a self-peeling gallium nitride crystal, comprising the steps of:

(1) preparing a GaN substrate with an inverted hexagonal pyramid structure and exposed semi-polar surfaces {10-11} or {11-22 };

(2) preparing an electrode on the GaN substrate with the exposed semi-polar surface;

(3) selecting metal capable of being electrolytically reduced to prepare a corresponding metal salt solution or metal salt solution;

(4) assembling a metal electrodeposition circuit, connecting the GaN substrate with the electrode exposed semipolar surface to the negative electrode of a direct current power supply, selecting other electrodes to be connected with the positive electrode of the direct current power supply, and putting the connected positive and negative electrodes into the prepared metal salt solution or metal salt solution;

(5) controlling voltage or current, and selecting deposition time to obtain a pretreated GaN substrate with metal deposition;

(6) putting the pre-treated substrate with metal deposition into deionized water, and carrying out long-time ultrasonic treatment to remove the deposited metal weakly connected with the surface of the GaN substrate to obtain the GaN substrate with a semi-polar surface shielded by the metal;

(7) the substrate was subjected to growth of a GaN single crystal.

2. The method of claim 1, wherein: the GaN crystal in the step (1) comprises a GaN single crystal or a single crystal thin film.

3. The method of claim 1, wherein: the method for preparing the GaN substrate with the inverted hexagonal pyramid structure and the exposed semi-polar surface {10-11} or {11-22} in the step (1) comprises but is not limited to chemical etching, plasma etching and pyrolysis.

4. The method of claim 1, wherein: the method for preparing the electrode on the GaN substrate in the step (2) comprises and is not limited to indium grain welding, silver adhesive curing bonding and conductive adhesive tape bonding.

5. The method of claim 1, wherein: the metal that can be electrolytically reduced in the step (3) includes, but is not limited to, Mg, Al, Zn, Fe, Cu or Ag.

6. The method of claim 1, wherein: the metal-corresponding metal salt that can be electrolytically reduced in the step (3) includes, but is not limited to, chloride, sulfate and nitrate.

7. The method of claim 1, wherein: the preparation of the metal salt solution (melt) in the step (3) includes, but is not limited to, deionized water dissolution and high-temperature melting, and the solution concentration is 0.1 mol/L-1 mol/L.

8. The method of claim 1, wherein: the positive electrode selected in the step (4) includes, but is not limited to, a carbon rod, a high-purity metal, and an alloy thereof.

9. The method of claim 1, wherein: and (5) controlling the power supply voltage to be 2-15V.

10. The method of claim 1, wherein: and (5) controlling the power supply current to be 0.3-0.8A.

Technical Field

The invention relates to a method for preventing a semi-polar surface of a gallium nitride seed crystal layer from merging and growing a self-stripping gallium nitride (GaN) crystal. The method is simple, convenient, direct and easy to operate, can prepare a processing substrate used for growing the self-stripping GaN crystal, and belongs to the technical field of photoelectrons.

Background

GaN is a representative of third generation semiconductors and has found widespread use in high frequency, high power devices. However, most of the currently used GaN-based devices are fabricated by means of heteroepitaxy, which has a high dislocation density and residual stress of the grown GaN crystal due to lattice mismatch and thermal mismatch between GaN and the substrate, and thus, the performance of the GaN-based devices is seriously affected. Pretreatment of the substrate to reduce dislocations and stresses in the GaN single crystal is a key technique for growing high quality GaN single crystals.

The current methods for pretreating GaN substrates have several major success cases: oshima et al (2002) researches and develops a vacancy-assisted separation technology, namely TiN with a nano-network structure is prepared on an initial substrate grown by MOCVD (metal organic chemical vapor deposition), then GaN is grown by taking the TiN as the substrate, and finally a high-quality GaN epitaxial layer with low dislocation density is obtained; kensaku Motokit et al (2007) researches on improving growth of the inverted hexagonal pyramid epitaxial crystal defect reducing method to obtain a GaN crystal with low defect density; lei Zhang et Al (2014) developed a two-dimensional material coating method in MOCVD-GaN (Al)₂O₃) The substrate is coated with graphene and BN, and GaN crystal is blockedDislocation extension in the growth process reduces the dislocation density and improves the crystal quality; moosun Lee et al (2017) etched a substrate using HCl gas to prepare a porous structure substrate, and grown to obtain a GaN crystal with a thickness of approximately 5 mm. The methods play a certain role in generating high-quality GaN single crystals, but the process is complex, more auxiliary instruments and equipment are needed, and the popularization and the use are not facilitated.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for hindering the growth of semipolar plane gallium nitride and preparing self-stripping gallium nitride crystal aiming at the defects of the prior art.

The invention relates to a method for hindering growth of semipolar plane gallium nitride and preparing self-stripping gallium nitride crystal, which comprises the following steps:

(1) preparing a GaN substrate with an inverted hexagonal pyramid structure and exposed semi-polar surfaces {10-11} or {11-22 };

(2) preparing an electrode on the GaN substrate with the exposed semi-polar surface;

(3) selecting metal capable of being electrolytically reduced to prepare corresponding metal salt solution (molten liquid);

(4) assembling a metal electrodeposition circuit, connecting a GaN substrate with electrodes and exposed semipolar surfaces to the negative electrode of a direct-current power supply, selecting other electrodes to be connected with the positive electrode of the direct-current power supply, and putting the connected positive and negative electrodes into a prepared metal salt solution (molten liquid);

(5) controlling voltage or current, and selecting proper deposition time to obtain a pretreated GaN substrate with metal deposition;

(6) putting the pre-treated substrate with metal deposition into deionized water, and carrying out long-time ultrasonic treatment to remove the deposited metal weakly connected with the surface of the GaN substrate to obtain the GaN substrate with a semi-polar surface shielded by the metal;

(7) the GaN single crystal is grown on the substrate by an HVPE method, metal gallium with the purity of 7N is used as a Ga source, ammonia gas with the purity of 6N is used as an N source, HCl with the purity of 5N is usually used as an initial reaction gas, high-purity nitrogen or hydrogen is selected as a transport gas, and the GaN single crystal can be epitaxially grown on the substrate by reacting Ga-containing primary reaction products (mainly gallium chloride gas) with the ammonia gas under relatively mild conditions (the reaction pressure is 1atm, and the reaction temperature is about 1000 ℃).

The GaN crystal in the step (1) comprises a GaN single crystal or a single crystal thin film.

The method for preparing the GaN substrate with the inverted hexagonal pyramid structure and the exposed semi-polar surface {10-11} or {11-22} in the step (1) comprises but is not limited to chemical etching, plasma etching, pyrolysis and the like.

The method for preparing the electrode on the GaN substrate in the step (2) comprises and is not limited to indium grain welding, silver adhesive bonding and conductive adhesive tape bonding.

The metal that can be electrolytically reduced in the step (3) includes, but is not limited to, Mg, Al, Zn, Fe, Cu, Ag, and the like.

The metal corresponding metal salt that can be electrolytically reduced in the step (3) includes, but is not limited to, chloride, sulfate, nitrate, and the like.

The preparation of the metal salt solution (melt) in the step (3) includes, but is not limited to, deionized water dissolution and high-temperature melting, and the solution concentration is 0.1 mol/L-1 mol/L.

The positive electrode selected in the step (4) includes, but is not limited to, a carbon rod, a high-purity metal, an alloy thereof, and the like.

And (5) controlling the power supply voltage to be 2-15V.

And (5) controlling the power supply current to be 0.3-0.8A.

The deposition time in the step (5) is controlled to be 3-15 min.

And (4) the ultrasonic time of the GaN substrate pretreated in the step (6) in deionized water is 30-60 min.

According to the invention, by the method of depositing metal on the semipolar surface, an obstruction structure is formed only on the semipolar surface of the sample, and by means of the vacancy auxiliary separation principle, the prepared processing substrate is beneficial to relieving the stress in the crystal and realizing the self-peeling of the crystal in the later growth process of the GaN body single crystal. Compared with the prior art, the method has the characteristics of simple process, convenience in operation, low cost and strong practicability, has the advantages of mild reaction conditions, simplicity and convenience in operation and the like, has important significance for further improving the quality of the GaN single crystal, and is suitable for industrial implementation.

Drawings

FIG. 1 is an SEM image of the surface topography of a GaN substrate having an inverted hexagonal-pyramid structure and exposed semi-polar planes {10-11} or {11-22} prepared in example 1.

FIG. 2 is an SEM image of the cross-sectional morphology of a GaN substrate having an inverted hexagonal-pyramid structure with the semi-polar plane exposed {10-11} or {11-22} prepared in example 1.

FIG. 3 is an SEM image of the surface topography of a GaN substrate of example 1 after metal deposition at a voltage of 5V on the substrate, wherein the GaN substrate has an inverted hexagonal pyramid structure and the semi-polar face {10-11} or {11-22} is exposed.

FIG. 4 is an SEM image of the cross-sectional morphology of a single etch or dissolution pit after ultrasonication of a metal deposited on a GaN substrate having an inverted hexagonal pyramid structure with exposed semi-polar planes {10-11} or {11-22 }.

Detailed Description

The present invention will be described in detail with reference to specific examples.

Example 1

(1) Adopting a hydrothermal corrosion method to corrode the GaN to prepare a GaN substrate with an inverted hexagonal pyramid structure and exposed semi-polar surfaces {10-11} or {11-22 };

(2) selecting a high-purity copper wire with the diameter of 0.1mm as a connecting wire, firstly adhering the copper wire to the surface of the GaN substrate by using silver colloid, and then transferring the substrate to an oven with the temperature of 80-150 ℃ for curing until the silver colloid is completely solidified;

(3) 13.630g of zinc chloride is weighed and dissolved in 100ml of deionized water to obtain ZnCl with the concentration of 1mol/L₂The solution is used as a metal salt solution to be electrolyzed;

(4) PSW 160-14.4 is selected as a direct current power supply, a platinum electrode is selected as an anode of electrolysis, a GaN substrate fixed with a lead is selected as a cathode of the electrode, the anode and the cathode are connected with the power supply by the lead, and the anode and the cathode are infiltrated into ZnCl₂A solution;

(5) controlling the direct current voltage to be 5V, the corresponding current to be 0.3A and the electrolysis time to be 10min to obtain a pre-treated GaN substrate with metal deposition;

(6) and putting the pre-treated substrate with metal deposition into deionized water, and carrying out ultrasonic treatment for 45min to remove the deposited metal weakly connected with the surface of the GaN substrate to obtain the GaN substrate with the semi-polar surface shielded by the metal.

(7) Growing a GaN single crystal on the substrate by an HVPE method, wherein metal gallium with the purity of 7N is used as a Ga source, ammonia gas with the purity of 6N is used as an N source, HCl with the purity of 5N is usually used as an initial reaction gas, and high-purity nitrogen or hydrogen is selected as a transport gas, so that the GaN single crystal can be epitaxially grown on the substrate by reacting a Ga-containing primary reaction product (mainly gallium chloride gas) with ammonia gas under relatively mild conditions (the reaction pressure is 1atm, and the reaction temperature is about 1000 ℃); and obtaining the self-stripping GaN crystal after the crystal growth is finished.

FIG. 1 shows that a large number of hexagonal etching pits with a size of about 2 μm are formed on the surface of a substrate after hydrothermal etching; FIG. 2 shows that the etching has penetrated into the sapphire substrate surface and there is more erosion space at the interface; fig. 3 and 4 show that after electrodeposition and ultrasonication, the surface of the etched substrate has no metal adhesion, while the walls of the hexagonal etch pits have a large amount of metal adhesion, forming a metal shadow of the semipolar surface.

Example 2

Except that a GaN substrate having an inverted hexagonal pyramid structure with the semi-polar plane {10-11} or {11-22} exposed was prepared using concentrated phosphoric acid etching in step (1) as described in example 1;

example 3

Except that a GaN substrate having an inverted hexagonal pyramid structure with the semi-polar plane {10-11} or {11-22} exposed was prepared using pyrolysis in step (1) as described in example 1;

example 4

As described in example 1, except that indium particles were used for wire bonding in step (2);

example 5

As described in example 1 except that the wires are bonded using a conductive adhesive in step (2);

example 6

As described in example 1, with the difference that in step (3) the ZnCl removal is selected₂Preparing reducible metal salt solution from chloride, sulfate and nitrate of Mg, Al, Zn, Fe, Cu and Ag metal;

example 7

As described in example 1, except that a carbon rod was selected as the positive electrode in step (4);

example 8

As described in example 1, except that the control voltage in step (5) was 10V;

it will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.