Method for growing gallium nitride monocrystals

FIELD: electrical engineering.

SUBSTANCE: according to the method, charge stock containing a gallium source and flux components is heated and maintained at the specified temperature or, alternatively, heated and slowly cooled down from the specified temperature inside a container, with a temperature gradient maintained between the upper and the lower parts of the container under a nitrogen-containing gas pressure. The flux, by way of core components, contains cyanides or cyanamides or dicyanamides of alkaline and/or alkaline-earth metals and modifying additives enhancing gallium nitride solubility and/or increasing growth rate and/or enabling control of physical properties of crystals obtained.

EFFECT: reduced rate of corrosion of the latter, improved quality of monocrystals obtained.

16 cl, 2 tbl

 

The invention relates to the growing technology of semiconductor materials and can be used to obtain single crystals of gallium nitride and solid solutions based on it.

The gallium nitride (GaN) is a promising semiconductor material for electronic industry, in particular for the production of white, blue and UV LEDs, lasers, ultraviolet sensors, power and high frequency electronics. Applications white led backlight mobile devices, automotive, industrial, traffic, domestic and architectural lighting. In all cases a decisive role in deciding how lighting plays an unmatched efficiency LEDs, which currently 50-60%, which is higher than that of incandescent lamps (7-11%) or gas discharge lamps (20-25%). Industrial production of single crystals of gallium nitride opens great prospects for microelectronics chips based on it will consume less energy, will increase the overall efficiency of electronic circuits. Monocrystalline gallium nitride promising as a material in the production of high-frequency and high-current transistors.

The number of known methods of growing single crystals of gallium nitride suitable for use in the electronics industry (EN 2315825, SU 1705425, EN 244549, EN 2097452, US 6592663, US 7459023).

There is a method of growing crystals of gallium nitride (EP 2103721, publ. 23.09.2009), which comprises reacting with nitrogen gallium, mixed melt containing alkali metal, gallium and carbon, thus causing the crystal growth of gallium nitride.

The closest in technical essence is a method for the production of single crystals of nitrides of elements of the third group (US 7507292, the filing date 30.06.2003, publ. 09.03.2006), which includes reacting at least one element of the third group, which includes gallium, aluminum and indium, nitrogen in the mixed molten sodium with another alkali metal (except sodium, preferably with lithium Li) or alkaline earth metal, thus causing the crystal growth of the nitride element of the third group. The method allows obtaining three-dimensional transparent single crystal of a nitride of the elements of the third group having a low dislocation density and high quality. In a preferred embodiment of the invention, the single crystal growth is made from melt-Na-Li-Ga at temperatures from 500°C to 1100°C and a pressure of from 0.1 MPa to 6 MPa. This technical solution chosen by the applicant as a prototype.

In these ways to increase the speed of crystal growth and improve their crystalline perfection of the need is to maintain a high concentration of lithium or alkaline-earth metals in the melt, which are reactive in relation to most construction materials used for the manufacture of containers (boron nitride, tungsten, molybdenum). This leads to chemical corrosion of the material of the container, its failure, as well as to contamination of the melt, and therefore the resulting substance, the corrosion products. The high corrosion rate of the materials of the container containing the melt is a significant disadvantage inherent in these methods, including the prototype.

For the information of the corrosion of the materials of the container containing the melt, for at least part of the flux components must be at least chemically inactive, and preferably chemically inert relative to the material of the container.

The task, which is aimed by the invention is a method of growing single crystals of gallium nitride with the composition of the flux, which is chemically inert to most construction materials used for the manufacture of containers.

The technical result is to reduce the rate of corrosion of the materials of the container containing the melt, as well as in improving the quality of single crystals of gallium nitride.

To achieve these objectives in the method of growing single crystals neath the IDA gallium, including heating and holding at a given temperature or heating and slow cooling from the set temperature in the container while maintaining a temperature gradient between the top and bottom parts of the container under the pressure of the nitrogen-containing gas mixture containing the gallium source and the components of the flux, according to the invention the flux contains as main components cyanide, or cyanamide, or dicyanamide alkaline and/or alkaline earth metals and modifying additives to increase the solubility of gallium nitride and/or increasing the growth rate and/or to control the physical properties of the obtained crystals.

Cyanide is an inorganic compound containing the group CN-. Cyanamide-inorganic compounds containing the group CN2-2. Experiments have shown that cyanide and cyanamide alkali and alkaline earth metals in molten form is chemically inert relative to that used in the known methods for producing gallium nitride materials container (boron nitride, tungsten, molybdenum). Used molten cyanides, cyanamide and dicyanamide alkali and alkaline earth metals do not interact even with iron, much less chemically resistant material than boron nitride, tungsten, molybdenum. Thus, the proposed composition of the flux is him who Cesky inert to most structural materials, used for the manufacture of containers (boron nitride, tungsten, molybdenum), and therefore significantly decreases the interaction of the components of the flux with the container material, which helps prevent corrosion of the materials of the container and contamination of the melt by corrosion products, as well as improving the quality of single crystals of gallium nitride.

As a flux may be used cyanide, or cyanamide, or dicyanamide one or more alkali metals (Li, Na, K, Rb, Cs) in an amount of from 1 to 99 wt.%. In a preferred embodiment of the invention, the lithium cyanamide cyanide or sodium cyanamide.

As a flux can also be used cyanide, or cyanamide, or dicyanamide one or more alkaline earth metals (Be, Mg, Ca, Sr, Ba) in an amount of from 1 to 99 wt.%. Most preferred is the use of barium cyanamide BaCN2.

As a flux can also be used a mixture of cyanide, or cyanamide, or dicyanamide one or more alkali metals and simultaneously cyanide, or cyanamide, or dicyanamide one or more alkaline earth metals in an amount of from 1 to 99 wt.%.

In a preferred embodiment of the invention, cyanide, or cyanamide, or dicyanamide alkaline or alkaline earth metals in flucanozole from 20 to 80 wt.%. Experimentally established that the ratio of the share of components in the flux provide the most optimal conditions of the process of growing single crystals of gallium nitride.

As modifying additives to increase the solubility of gallium nitride and/or increasing the speed of his growing single crystals can be used:

- one or more alkali metals except lithium (metal sodium, potassium, rubidium and cesium) in an amount of from 1 to 99 wt.%,

- lithium or nitride in an amount of from 0.01 to 50 wt.%,

- one or more alkaline earth metals or their nitrides in an amount of from 0.01 to 50 wt.%,

- one or more alkali metals and simultaneously one or more alkaline earth metals or their nitrides in an amount of from 0.01 to 50 wt.%.

Thus, the total number of supplements lithium and alkaline earth metals or nitrides of lithium and alkaline earth metals should not exceed 50 wt.% from the mass flux. Higher lithium content and alkaline earth metals and their nitrides lead to lack of growth of single crystals of gallium nitride preferable in view of such conditions, the formation of compounds of gallium type Li3GaN2, Mg3Ga2N4Ca3Ga2N4, Sr3Ga2N4, Ba3Ga2N4

Most preferred is the use of lithium or its nitride, which have the highest solubility in melts.

Other modifying additives allow legitemate the single crystal impurities and thereby to control its physical properties, including electrical conductivity, conductivity type, carrier concentration, the spectral characteristics of LEDs and lasers based on single crystals.

As such modifying agents may be used one or more elements or compounds from the group consisting of B, Al, In, Li3BN2, Li3GaN2in total amount of from 0.01 to 50 wt.% from the mass flux, items IV, V, VI and VII groups, rare-earth and transition metals in a total amount of from 0.001 to 10 wt.% from the mass flux. The biggest change properties cause AlN additives and Fe due to their higher solubility in the GaN crystals.

As the source of gallium can be used polycrystalline or amorphous gallium nitride in pure form or in the form of a solid solution thereof or a mixture of aluminum nitride in the total amount of 5-95 wt.% from the total mass of the contents of the container.

The process is conducted at a temperature of 600-1100°C and a pressure of nitrogen gas of 0.1 to 200 ATM. The temperature gradient between the top and bottom parts of the container sostav the et from -0,1 to -100°C or 0.1 to 100°C.

As the nitrogen-containing gas can be used gaseous nitrogen (N2), or gaseous ammonia (NH3), or a mixture of gaseous nitrogen (N2) and gaseous ammonia (NH3).

Before beginning the process of growing a single crystal gallium nitride in the container is injected seed, representing a single crystal gallium nitride small size, which is used for the growth of the single crystal to a larger size. Introduction into the container of the seed provides a more rapid growth of the single crystal due to the higher initial square, which grows at a constant linear speed of the new material.

The proposed method for the production of bulk single crystals of gallium nitride is grown single crystal due to transportation reactions leading to the migration of gallium nitride from the hot zone of the container containing polycrystalline gallium nitride, in the cold zone. The gallium nitride presumably transported in the following reversible chemical reaction:

GaN+Li3N ↔ Li3GaN2

The resulting Li3GaN2soluble to a significant extent in the melt on the basis of cyanide or cyanamide alkali and alkaline earth metals. The difference of the proposed method of growing single crystals of gallium nitride from the known method, wybranego as a prototype, is that part of the flux of alkali and alkaline earth metals are replaced by cyanide or cyanamide of the respective metals.

The content of gallium metal in the flux, in contrast to all prototypes, declaring the concentration range from 0.01 to 99.99 wt.%, is 0.00 wt.%. This prevents saturation of the flux with respect to the formation of gallium nitride and to avoid generation of spurious crystals on the surface of the container, which contributes to improving the quality of single crystals of gallium nitride.

Patent research has not revealed any technical solutions, characterized by the claimed combination of features, therefore, it can be assumed that the technical solution meets the concept of "novelty".

Using a combination of distinctive features is also not known, which indicates the criterion of "inventive step".

In addition, the proposed solution can be produced on an industrial scale and will find application in particular in the production of single crystals of gallium nitride and solid solutions on its basis, i.e. characterized by the criterion of "industrial applicability".

The proposed method of growing single crystals of gallium nitride is as follows.

In the container being in Azot the th atmosphere inside the unit, to heat the crucible to 1100°C and a nitrogen pressure of 200 ATM, put a layer of polycrystalline gallium nitride and flux components in the desired ratio, such as, for example, in table 1, heated to a temperature of 750-900°C and incubated for 50-300 hours at the temperature gradient between hot and cold zones of the container from 0.01°C to 100°C. the Growing single crystal is due to the transport of reactions leading to the migration of gallium nitride from the hot zone of the container containing polycrystalline gallium nitride, in the cold zone.

During the process of growing a single crystal gallium nitride instead of excerpts of the container at a given temperature may be a slow decline in the average temperature of the container from the maximum initial temperature (for example, 850°C) and minimum temperature (for example, 800°C).

This method can be used for growing single crystals of gallium nitride, and to obtain solid solutions based on it.

Examples of compositions of components for growing single crystals of gallium nitride are shown in table 1. Examples of conditions in the container and the characteristics of the obtained crystals are shown in table 2.

Table 1
An example of the compositions of components for growing single crystals of gallium nitride
№ p/pGaN, G.Li2CN2gNa2CN2gNa, gLi3N, gNaC2N3gBaCN2gKCN, gBa, gOther, g
11,4055,136,447
22,4686,3247,118
31,3674,6913,1633,437
41,2833,5212,958RUB 3.6740,438
51,8525,4470,380,129
62,0734,5382,4960,6230,261
71,5384,3290,2480,187
82,2174,1951,7830,341
91,7215,273of 0.3370,578 AlN
101,9134,5861,2780,3480,172to 0.127 Fe

Table 1 (continued)
Examples of compositions of components for growing single crystals of gallium nitride
№ p/pGaN, gLi2CN2gNa, gLi, gNaCN, gBa(CN)2gCa(C2N3)2g
111,9534,5510,3310,376
122,4714,3461,2240,1870,571
131,4495,7130,5280,2120,334
141,9523,8640,2890,125

Alternative as components for growing the single crystal is in gallium nitride can be used cyanide, cyanamide or dicyanamide other alkaline or alkaline earth metals, in addition to the components shown in table 1. For example, cyanamide Mg, Ca, dicyanamide Li. Cyanide is less convenient, since they require additional precautions due to their toxicity.

As modifying additives can be used other than those specified in table 1, Supplement. For example, Ca, Ca3N2, Sr, SrN, as well as In, BN, Li3GaN2, NaCl, Mo, TA, Zr, W, Co, but they showed less noticeable effect on the properties of as-grown single crystals.

Implementation of the proposed method is illustrated by the following examples.

In a tungsten container with a volume of 20 ml in the atmosphere of pure nitrogen, was placed a layer of polycrystalline gallium nitride in the amount indicated in table 1, and then the components of the flux Li2CN2, Na2CN2and other in the amount indicated in table 1. The container is placed in an oven, cover and raise the pressure of pure nitrogen in a furnace to a specified in table 2. Then raise the temperature T in the oven until specified in table 2 so that the upper portion of the container had a temperature below the bottom of the container by the amount ΔT specified in table 2. The data of the temperature and pressure constant support during the time specified in table 2. Then reduce the oven temperature to anatoy, reduce the pressure to atmospheric, remove the container from the oven and remove from the container, the single crystals after washing with water contents of the container. The resulting crystals of gallium nitride with characteristics listed in table 2. The thickness of the layer of corrosion products on the surface of the container in all cases did not exceed 0.1 mm, which demonstrates the chemical compositions relative to the material of the container.

Therefore, the task of creating a method of growing single crystals of gallium nitride with the composition of the flux, which is chemically inert to most construction materials used for the manufacture of containers, solved through the use in the flux of cyanide, or cyanamide, or dicyanamide alkali and alkaline earth metals, which is chemically inert with respect to construction materials of the container. The result is a reduction in the rate of corrosion of the materials of the container containing the melt, as well as improved quality single crystals of gallium nitride by reducing pollution derived substances with corrosion products.

The proposed method, in addition, provides high speed growth of single crystals of gallium nitride and such properties of the obtained single crystals, as transparency (examples 1-9 and 11-14), n is ska density of dislocations (10 2-104cm-2for all examples), the three-dimensional shape of the crystals (prisms and pyramids), large size (up to 0.5 mm).

1. Method of growing single crystals of gallium nitride, comprising heating and holding at a given temperature or heating and slow cooling from the set temperature in the container while maintaining a temperature gradient between the top and bottom parts of the container under the pressure of the nitrogen-containing gas mixture containing the gallium source and the components of the flux, wherein the flux contains as main components cyanide, or cyanamide, or dicyanamide alkaline and/or alkaline earth metals and modifying additives to increase the solubility of gallium nitride, and/or increasing the growth rate, and/or to control the physical properties of the obtained crystals.

2. The method according to claim 1, characterized in that as a flux use cyanide, or cyanamide, or dicyanamide one or more alkali metals Li, Na, K, Rb, Cs.

3. The method according to claim 1, characterized in that as a flux use cyanide, or cyanamide, or dicyanamide one or more alkaline earth metals Be, Mg, Ca, Sr, Ba.

4. The method according to claim 1, characterized in that as a flux, a mixture of cyanide, or cyanamide, or dicyanamide one or more alkali metals and the simultaneous cyanide, or cyanamide, or dicyanamide one or more alkaline earth metals.

5. The method according to claim 1, characterized in that as a modifying additive use lithium or nitride in an amount of from 0.01 to 50 wt.%.

6. The method according to claim 1, characterized in that as modifying additives use one or more alkali metals except lithium in an amount of from 1 to 99 wt.%.

7. The method according to claim 1, characterized in that as modifying additives use one or more alkaline earth metals or their nitrides in an amount of from 0.01 to 50 wt.%.

8. The method according to claim 1, characterized in that as modifying additives use one or more alkali metals and simultaneously one or more alkaline earth metals or their nitrides in an amount of from 0.01 to 50 wt.%.

9. The method according to claim 1, characterized in that as modifying additives use one or more elements or compounds from the group consisting of B, Al, In, Li3BN2, Li2GaN2in total amount of from 0.01 to 50 wt.%, items IV, V, VI and VII groups, rare-earth and transition metals in a total amount of from 0.001 to 10 wt.%.

10. The method according to claim 1, characterized in that as the source of gallium using polycrystalline or amorphous gallium nitride in the total amount of 5-95 wt.% from the total mass is possessed of the container.

11. The method according to claim 1, characterized in that as the source of gallium using polycrystalline or amorphous gallium nitride in the form of solid solution on the basis of the total amount of 5-95 wt.% from the total mass of the contents of the container.

12. The method according to claim 10, characterized in that the polycrystalline or amorphous gallium nitride mixed with aluminum nitride in the total amount of 5-95 wt.% from the total mass of the contents of the container.

13. The method according to claim 1, characterized in that the process is conducted at a temperature of 600-1100°C and a pressure of nitrogen gas of 0.1 to 200 ATM.

14. The method according to claim 1, characterized in that the temperature gradient between the top and bottom parts of the container is between -0,1 and -100°C or 0.1 to 100°C.

15. The method according to claim 1, characterized in that as the nitrogen-containing gas used is nitrogen gas or ammonia gas or a mixture of gaseous nitrogen and gaseous ammonia.

16. The method according to claim 1, characterized in that before starting the process of growing a single crystal gallium nitride in the container is injected seed, representing a single crystal gallium nitride small size, which is used for the growth of the single crystal to a larger size.



 

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SUBSTANCE: invention relates to production of synthetic superhard materials, particularly, polycrystalline cubic boron at high pressure and temperature to be sued in chemical, electronic and other industries. Proposed method comprises preparing mix of wurtzite-like and cubic modifications in relation of 1:4 to 2:1, respectively, processing it in planet mill for mechanical activation and crushing to grain size not exceeding 1 mcm, forming and annealing the mix at 1400-1800°C and 7.0-9.0 GPa, keeping at annealing temperature for time defined by conditions of transition on boron nitride wurtzite modification into cubic one without recrystallisation, equal to 5-30 s. Accurate time of keeping at preset temperature and pressure is defined proceeding from necessity of preservation of 5 to 15% of wurtzite boron nitride amount in initial mix.

EFFECT: lower temperature, pressure and duration of synthesis, improved mechanical and physical properties.

2 cl, 5 ex, 1 tbl

FIELD: chemistry.

SUBSTANCE: method of growing crystals of group III metal nitrides from a gas phase involves placing a substrate 12 into the top part of a reactor over a source of a group III metal 5 and feeding gas streams to the surface of the substrate 12 in a direction opposite the direction of force of gravity, each containing at least one chemically active gas and at least one carrier gas. To increase efficiency of the process, consumption of chemically active gases meets the following condition: Gv/GIII=5÷1000, where Gv is molar consumption of chemically active gases containing a group V element - nitrogen, for example ammonia, GIII is molar consumption of chemically active gases containing a group III metal. Each chemically active gas is mixed with at least one carrier gas until obtaining gas streams in which overall density of the gas mixture containing chemically active gas which contains a group III metal, is less than overall density of a gas mixture containing chemically active gas which contains a group V element - nitrogen. Such a ratio of densities of gas mixtures improves the structure of gas streams in the reactor and enables to eliminate vortex recirculating flow under the substrate. The obtained gas streams are then fed in the direction of the substrate 12 through annular channels 8, 9, 10, formed symmetrically about the axis of the reactor.

EFFECT: improved quality of crystals and controllability of the process owing to improved structure of gas streams in the reactor.

4 cl, 4 dwg

FIELD: chemistry.

SUBSTANCE: method is realised through slow evaporation of ammonia from 5% aqueous ammonia solution of fine-crystalline silver azide powder at normal conditions in a crystalliser through 0.5 mm diametre holes in a polyethylene film covering the crystalliser, at a rate of 0.407 g/day. The crystalliser containing the solution is placed between two electrodes in a non-contact electric field with strength of 100 - 106 V/cm.

EFFECT: by varying the electric field strength during crystallisation, crystals of different sizes can be obtained, having minimal content of defects, better working characteristics and longer storage life.

1 ex, 1 tbl, 6 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to production of materials capable of intense emission of light in a broad spectral range under the effect of photo-, electron- and electro-excitation, where the emission is stable at high temperature, radiation and in chemically aggressive media. The invention can be used in making light emitters and radiation detectors. A growth mixture based on hexagonal boron nitride is mixed with activators - rare earth metal compounds whose melting point is lower than fusion point of cubic boron nitride, in amount of 0.05-15% of the weight of the growth mixture. The mixture is then exposed to high pressure and temperature. Cubic boron nitride is obtained in form of micropowder, powder, crystals and ceramic samples. Gadolinium compounds are used the activator to obtain light emission in the ultraviolet range; cerium compounds are used to obtain emission in the ultraviolet, blue and yellow ranges; samarium compounds are used for the orange range; neodymium, praseodymium, erbium, ytterbium or holmium compounds are used to obtain emission in the infrared range. To obtain cubic boron nitride having electroluminescence, sulphur or selenium is added to the mixture.

EFFECT: invention widens the spectral range of light emission of cubic boron nitride.

7 cl, 3 dwg, 14 ex

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