CN1113988C - Hydrothermal growth method of gallium nitride single crystal - Google Patents

Abstract

The invention relates to a method for growing gallium nitride single crystal. In the invention, an inert material lining is added to the inner cavity wall of the autoclave, and a temperature field is provided by a temperature control system, so that gallium nitride single crystal is grown in ammonia heat. The temperature and pressure of the invention are not too high (the temperature is 400-600° C., and the pressure is 1000-1800 bar), the equipment is simple, the cost is low and efficient, the yield of gallium nitride is high, and it is convenient for industrial batch production of GaN single crystal material. The diameter of the grown gallium nitride single crystal is greater than 20 μm, and the length is on the order of millimeters, which has great practical value.

Description

A kind of hydrothermal growth method of gallium nitride single crystal

The invention relates to a crystal growth method, in particular to a gallium nitride single crystal growth method.

GaN is an excellent wide-bandgap semiconductor material with a bandgap width of 3.4eV at room temperature. It is an ideal material for making blue and green light-emitting diodes and laser diodes. This type of light source has broad application prospects and huge economic benefits in optical information storage, high-speed laser printing, optical display, signal detection, and medicine.

At present, MOCVD (metal organic chemical vapor deposition) is mostly used to produce GaN semiconductor films to manufacture laser diodes. For example, trimethylgallium, ammonia (NH ₃ ) and dicyclopentadienyl Magnesium (bis-cyclopentadienyl magnesium) gas is supplied to the white sapphire substrate. The substrate is heated to 1000°C to react the above-mentioned raw material gases to form a Mg-doped GaN film on the substrate surface. After growing into a thin film, the thin film is irradiated with a low-energy electron beam to obtain a p-type semiconductor (document 1. H. Amano, et al. Jpn. J. Appl. Phys. Vol. 28 (1989) L2112). As we all know, the price of MOCVD equipment is very high, and the output is not large, so it is difficult to reduce production costs and realize real large-scale industrial production. At the same time, the lowest dislocation density of this GaN heteroepitaxial layer is as high as 10 ⁸ /cm ² . Among all known substrate materials, GaN single crystal substrate is the best substrate for producing blue laser diodes. Homoepitaxial growth on single crystals of GaN is the best way to reduce this dislocation density. In addition, self-connecting diodes on gallium nitride single crystals is the best way to make blue laser diodes. Therefore, it is of great significance to grow large-sized GaN single crystals. However, bulk single crystals of GaN cannot be grown from stoichiometric melts by existing methods such as Chowklarski or Bridgman, mainly due to the extremely high melting temperature of GaN, And it has a high equilibrium decomposition pressure when melting. General melt growth equipment cannot meet such stringent requirements, and it is almost impossible to grow semiconductor-quality crystals under such temperature and pressure. Therefore, gallium nitride single crystal must be grown by a method capable of lowering the growth temperature.

Poland's S.Porowski and I.Grzegoryz (document 2.J.Cryst.GrowthVol.178(1997)p.174) disclosed a method of growing flake-like GaN monolayers from a Ga solution system filled with high-pressure _N2 at high temperature. Crystallization method, the temperature and pressure are as high as 1400-1600 °C and 10-20 kbar, respectively. Such very harsh process conditions are difficult to achieve in general laboratories, let alone industrialized mass production.

China's Chen Xiaolong et al. proposed a hydrothermal growth method for growing GaN powders, and GaN nanopowders were grown at a relatively low temperature of 300-400°C (document 3. Chen Xiaolong et al., Chinese Invention Patent, Application No. 98125641.4). Because this kind of powder is suitable for spraying on the substrate to make GaN thin films and nano-semiconductor devices, it cannot be directly used as a substrate material for homoepitaxial growth and to make laser diodes. Therefore, it is necessary to find a method that can grow GaN at low temperature. single crystal method.

Poland's R.Dwilinski et al. (document 4.Acta Phys.Pol., A Vol.90 (1996) 763; Vol.88 (1995) 833) put Ga and liquid NH ₃ into the autoclave, in LiNH ₂ or Under the condition of K as a mineralizer, GaN can be grown below 500°C and 5Kbar. Although single crystals as long as 25 μm appear, the products are mainly GaN powder and ceramic-like materials, and the yield of single crystals is very low.

US APPurdy (document 5.Chem.Mater.Vol.11 (1999) 1648) uses NH ₃ and metal Ga in a quartz tube, under the action of NH ₄ I mineralizer, under the conditions of 10000psi and about 500°C, Cubic GaN and hexagonal GaN single crystals of 4 μm are grown on the quartz tube wall. Purdy also used NH ₄ Br and NH ₄ Cl as mineralizers, and used GaI and NH ₃ to generate GaN deposition films under similar conditions. However, the size of the grown single crystal is small (about 4 μm), which can only be used for scientific research without much application value.

The purpose of the present invention is to overcome the shortcomings of the prior art, by adding a liner to the inner cavity wall of the autoclave, and using a temperature control system to provide a temperature field, thereby growing gallium nitride single crystal in the hot liquid. The temperature and pressure of the invention are not too high, the equipment is simple, the cost is low and the efficiency is high, and it is convenient for industrial batch production of GaN single crystal material. The diameter of the grown gallium nitride single crystal is greater than 20 μm, the length is on the order of millimeters, and the yield is high.

The purpose of the present invention is achieved like this: 1. the high-purity gallium metal 6 that will participate in reaction, ammonium halide salt 10, high-purity liquid ammonia 5 and the autoclave body 2 of lining 8 and sealing plug 1 thereof are attached to the cavity wall , sealing caps 3 are all put into a vacuum glove box, and the vacuum of the glove box reaches 10 ^-2 Torr to remove moisture and oxygen in the air. The lining material is non-reactive with gallium and can suppress nitrogen Inert materials for excessive nucleation of gallium, such as platinum, gold, iridium, BN, AlN, etc., in order to prevent the liquid ammonia 5 from vaporizing rapidly, the autoclave body 2 used here is cooled with liquid nitrogen before being placed in a vacuum glove box middle. 2. In a vacuum glove box, weigh high-purity gallium metal 6 and ammonium halide salt 10 (such as NH ₄ Cl, NH ₄ Br, NH ₄ F or NH ₄ I) at a molar ratio of 8:2 to 9:1, It is then loaded into the autoclave body 2, where the ammonium halide salt 10 acts as a mineralizer. 3. Pour the high-purity liquid ammonia 5 according to the fullness of 65-90%. 4. Immediately install the sealing plug 1 and the sealing cap 3 on the autoclave body 2, tighten them, and perform a preliminary seal to avoid high-purity liquid ammonia as much as possible. The vaporization of ammonia 5 is lost, and all operations should be carried out quickly. 5. Further seal the autoclave on the sealing bench. 6. Take out the sealed autoclave, put it into a two-stage resistance heating furnace 4, control the heating by thermocouple 7 to 400-600°C, and use the temperature control system to make the temperature difference between the upper and lower parts of the autoclave 20 -150°C, this temperature difference produces the driving force required for crystallization of single crystals. 7. After 3 to 6 days at constant temperature, a colorless and transparent hexagonal columnar product 9 can be obtained in the middle or upper part of the autoclave, with a diameter greater than 20 μm and a length of millimeter order. It is confirmed to be GaN single column by powder X-ray phase identification. crystal.

The temperature and pressure for growing gallium nitride single crystal in the present invention are not too high (the temperature is 400-600° C., and the pressure is 1000-1800 bar). The conditions are suitable for laboratory and industrial production, and the equipment is simple, and the yield of gallium nitride is high. High, suitable for industrialized mass production. The size of the grown single crystal reaches the order of millimeters, which has great practical value.

Below in conjunction with accompanying drawing and embodiment the present invention is described in detail:

Figure 1 is a schematic diagram of a hydrothermal reaction system for growing GaN single crystals,

Figure 2 is the X-ray powder diffraction spectrum of the grown GaN single crystal,

Figure 3 is a photo of the grown GaN single crystal,

Among them: 1 sealing plug 2 autoclave body 3 sealing cap 4 resistance heating furnace

5 High-purity liquid ammonia 6 High-purity metal gallium 7 Thermocouple 8 Lining

9 GaN single crystal 10 ammonium halide salt

Example 1

Put the high-purity metal gallium 6 to be involved in the reaction, analytically pure NH ₄ Cl 10, and 50 ml of high-purity liquid ammonia 5 and a complete set of components of a cooled BN-lined autoclave with an inner diameter of Ф15 mm into a vacuum glove box During the process, the vacuum in the glove box was evacuated to 10 ^-2 Torr. In a vacuum glove box, weigh 3.15 grams of high-purity metal gallium 6 and 0.27 grams of NH ₄ Cl 10 in a molar ratio of 9:1 and put them into the autoclave body 2, and pour 540 milliliters of liquid ammonia into the autoclave according to the 65% fullness , in order to prevent the liquid ammonia 5 from rapidly vaporizing, the autoclave used here was previously cooled by liquid nitrogen. The sealing plug 1 and the sealing cap 3 of the autoclave are quickly installed on the autoclave body 2 and tightened to perform preliminary sealing. Lose all operations for avoiding the vaporization of liquid ammonia 5 as far as possible and should carry out rapidly. Take out the installed autoclave, further seal the autoclave on the sealing workbench, then put the sealed autoclave into the two-stage resistance heating furnace 4 and raise the temperature to 500°C, with a temperature difference of 100°C. After 5 days at constant temperature, a colorless and transparent hexagonal columnar crystal was obtained in an autoclave, which was identified as a GaN single crystal by X-ray phase identification.

Example 2

Put the high-purity metal gallium 6 to be involved in the reaction, analytically pure NH ₄ F 10 , high-purity liquid ammonia 5 and a complete set of components of a tubular autoclave with an inner diameter of Ф15mm and a platinum lining into a vacuum glove box, and evacuate the glove The degree of vacuum in the chamber was up to 10 ^-2 Torr. In a vacuum glove box, 4.17 grams of high-purity metal gallium 6 and 0.39 grams of NH ₄ F 10 are weighed in a molar ratio of 17:3 and packed into the autoclave body 2, and liquid ammonia 5 is poured into the autoclave according to a fullness of 70%. Make the liquefied ammonia 5 not vaporize rapidly, the autoclave body 2 used here is processed through liquid nitrogen cooling in advance, all operations should be carried out quickly for avoiding the vaporization of the liquefied ammonia 5 as far as possible; The cap 3 is mounted on the autoclave body 2 and tightened for preliminary sealing. The installed autoclave is taken out, and the autoclave is further sealed on the sealing workbench, and then the sealed autoclave is put into the two-stage resistance heating furnace 4 and the temperature is raised to 400 ° C, with a temperature difference of 20 ° C. After 4 days of constant temperature, a colorless and transparent hexagonal columnar crystal was obtained in the upper part of the autoclave, which was GaN crystal by phase analysis.

Example 3

Put high-purity metallic gallium 6 to be involved in the reaction, analytically pure NH ₄ Br 10, high-purity liquid ammonia 5 and a complete set of components of a tubular autoclave with an inner diameter of Ф15 mm and a gold lining into a vacuum glove box, and evacuate the glove The degree of vacuum in the chamber was up to 10 ^-2 Torr. Weigh 4.17 grams of high-purity gallium metal 6 and 1.46 grams of NH ₄ Br 10 in a vacuum glove box at a molar ratio of 4:1 and put them into the autoclave body 2, and pour liquid ammonia 5 into the autoclave body according to 90% fullness, In order to prevent the liquid ammonia 5 from rapidly vaporizing, the autoclave used here has been cooled by liquid nitrogen in advance. For avoiding the vaporization of the liquid ammonia 5 as much as possible, all operations should be carried out quickly; The cap 3 is mounted on the autoclave body 2 and tightened for preliminary sealing. The installed autoclave is taken out, and the autoclave is further sealed on the sealing workbench, and then the sealed autoclave is put into the two-stage resistance heating furnace 4 and the temperature is raised to 600°C, with a temperature difference of 150°C. After 4 days of constant temperature, a colorless and transparent hexagonal columnar crystal was obtained in the autoclave, which was GaN crystal by phase analysis.

Example 4

Put high-purity metal gallium 6 to be involved in the reaction, analytically pure NH ₄ I 10 , high-purity liquid ammonia 5 and a complete set of components of a tubular autoclave with an inner diameter of Ф15 mm and an AlN liner into a vacuum glove box, and evacuate the The vacuum degree of the glove box was up to 10 ^-2 Torr. In a vacuum glove box, 4.10 grams of high-purity gallium metal 6 and 1.64 grams of NH ₄ I 10 are weighed at a molar ratio of 4:1 and packed into the autoclave body 2, and poured into liquid ammonia 5 according to a 70% fullness, In order to prevent the liquid ammonia 5 from rapidly vaporizing, the autoclave used here has been cooled by liquid nitrogen in advance. For avoiding the vaporization of the liquid ammonia 5 as much as possible, all operations should be carried out quickly; The cap 3 is mounted on the autoclave body 2 and tightened for preliminary sealing. The installed autoclave is taken out, and the autoclave is further sealed on the sealing workbench, and then the sealed autoclave is put into the two-stage resistance heating furnace 4 and the temperature is raised to 450 ° C, with a temperature difference of 75 ° C. After 6 days of constant temperature, a colorless and transparent hexagonal columnar crystal was obtained in the autoclave, which was GaN crystal by phase analysis.

It should be pointed out that the above-mentioned embodiments only use four specific examples to illustrate the present invention, and it should not limit the present invention. Also, those skilled in the art know that various modifications not described herein can be made to the invention without departing from the spirit and scope of this patent.

Claims (2)

1, a kind of hot liquid method for growing of gallium nitride single crystal, used raw material is high purity metal gallium (6), halogenation ammonia salt (10), high-purity liquefied ammonia (5), it is characterized in that: may further comprise the steps: (1) will intend participating in reaction raw materials and internal chamber wall and all pack in the vacuum glove box with the autoclave body (2) of lining (8) and sealing plug (1) thereof, seal cap (3), and the vacuum tightness that makes this glove box of bleeding reaches the 10-2 torr, used lining is an inert material, and used autoclave body is handled through cooled with liquid nitrogen in advance; (2) in vacuum glove box, by 8: 2～9: 1 molar ratio weighing high purity metal gallium (6) and halogenation ammonia salt (10); (3) pour high-purity liquefied ammonia (5) into by 65～90% degree of filling; (4) immediately sealing plug (1) and seal cap (3) are contained on the autoclave body (2), tighten, and tentatively seal, all operations all is to carry out fast; (5) on the seal operation platform, autoclave is done further to seal; (6) autoclave sealed is taken out, put into a two-part resistance heading furnace (4),, and utilize temperature controlling system to make autoclave temperature head up and down be 20-150 ℃ by thermopair (7) control heat temperature raising to 400～600 ℃; (7) constant temperature is 3～6 days, can obtain water white hexagonal columnar product (9) on the middle part or the top of autoclave.

2, by the hot liquid method for growing of the described gallium nitride single crystal of claim 1, it is characterized in that: the lining of autoclave internal chamber wall (8) can be platinum, gold, iridium, BN or AlN.

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