A METHOD FOR PRODUCING MONOCRYSTALLINE GALLIUM CONTAINING NITRIDE AND MONOCRYSTALLINE GALLIUM CONTAINING NITRIDE, PREPARED WITH THIS METHOD

Abstract

The present invention relates to a method for producing monocrystalline gallium containing nitride from a source material containing gallium in the environment of supercritical ammonia solvent with the addition of a mineralizer containing the element of Group I (IUPAC, 1989), wherein in an autoclave two temperature zones are generated, i.e. a dissolution zone with lower temperature containing the source material, and a crystallization zone located below it with higher temperature, containing at least one seed. At least two further components are introduced into the process environment, namely an oxygen getter in molar ratio to ammonia ranging from 0.0001 to 0.2, and an acceptor dopant in molar ratio to ammonia not higher than 0.1, said acceptor dopant being manganese, iron, vanadium or carbon, or a combination thereof. The invention also relates to a monocrystalline gallium containing nitride prepared by this method.

Claims

1. The method for producing monocrystalline gallium containing nitride from a source material containing gallium in the environment of supercritical ammonia solvent with the addition of a mineralizer containing the element of Group I (IUPAC, 1989), wherein in an autoclave two temperature zones are generated, i.e. the dissolution zone with lower temperature containing the source material, and the crystallization zone located below it with higher temperature, containing at least one seed, the dissolution process of the source material and crystallization of gallium containing nitride on at least one seed is carried out, wherein at least two further components are introduced into the process environment, namely: a) the oxygen getter in the molar ratio to ammonia from 0.0001 to 0.2; b) the acceptor dopants in the mole ratio to ammonia of not more than 0.1; characterized in that the acceptor dopant constitutes manganese, iron, vanadium or carbon, or a combination thereof.

2. The method of claim. 1, characterized in that the acceptor dopant constitutes manganese in a molar ratio to ammonia from 0.000001 to 0.001, more preferably from 0.000005 to 0.0005, the most preferably from 0.00001 to 0.0001.

3. The method of claim. 1, characterized in that the acceptor dopant constitutes iron in a molar ratio to ammonia from 0.000001 to 0.01, more preferably from 0.00005 to 0.005, the most preferably from 0.0001 to 0.001.

4. The method of claim. 1, characterized in that the acceptor dopant constitutes vanadium in a molar ratio to ammonia from 0.000001 to 0.1, more preferably from 0.0005 to 0.05, the most preferably from 0.001 to 0.01.

5. The method of claim. 1, characterized in that the acceptor dopant constitutes carbon at a molar ratio to ammonia from 0.000001 to 0.1, more preferably from 0.00005 to 0.05, the most preferably from 0.0001 to 0.01.

6. A method according to any of the preceding claims, characterized in that the oxygen getter constitutes calcium or a rare-earth element, preferably gadolinium or yttrium, or a combination thereof.

7. A method according to any of the preceding claims, characterized in that the oxygen getter and acceptor dopant is introduced in the elemental form, i.e. metal or as a compound, preferably from the group comprising azides, amides, imides, amide-imides and hydrides, wherein the components are introduced separately or combined, in the case of combined introduction, mixtures of elements and compounds, intermetallic compounds or alloys are used.

8. A method according to any of the preceding claims, characterized in that the oxygen getter and/or acceptor dopant is introduced into the process environment with mineralizer.

9. A method according to any of the preceding claims, characterized in that the mineralizer contains sodium or potassium in a molar ratio to ammonia of from 0.005 to 0.5.

10. A method according to any of the preceding claims, characterized in that the stoichiometric gallium nitride—GaN is produced.

11. A method according to any of the preceding claims, characterized in that it is carried out in an autoclave having a capacity of more than 600 cm.sup.3, more preferably greater than 9000 cm.sup.3.

12. The monocrystalline gallium containing nitride, prepared with the method according to any of the preceding claims, comprising at least one element of Group I (IUPAC 1989) in an amount of at least 0.1 ppm, and contains oxygen in a concentration of not more than 1×10.sup.19 cm.sup.−3, preferably not more 5×10.sup.18 cm.sup.−3, and the most preferably not more than 1×10.sup.18 cm.sup.−3, characterized in that it is a highly resistive (semi-insulating) material having the resistivity greater than 1×10.sup.6 Ωcm, preferably greater than 1×10.sup.8 Ωcm and the most preferably greater than 1×10.sup.10 Ωcm.

13. The nitride according to claim 12, characterized in that it contains the acceptors selected from manganese, iron, vanadium or carbon, with a total concentration of not more than 1×10.sup.21 cm .sup.3, more preferably not more than 1×10.sup.20 cm .sup.3, the most preferably not more than 1×10.sup.19 cm.sup.−3, wherein the ratio of oxygen concentration to the total concentration of acceptors is not smaller than 1.2.

14. A nitride claim 12 or 13, characterized in that it is a stoichiometric gallium nitride GaN.

Description

ADVANTAGEOUS EXAMPLES OF APPLYING THE INVENTION

Example 1

Obtaining Semi-Insulating GaN (Ca:NH.SUB.3.=0.005; Mn:NH.SUB.3.=0.00015; Na:NH.SUB.3.=0.08)

[0041] The source material, i.e. 113.8 g (approx. 1.3 mol) of polycrystalline GaN containing 2.7 g of Ca (68 mmol) and 112 mg of Mn (2.05 mmol), was placed in a dissolution zone of a high pressure autoclave with a capacity of 600 cm.sup.3. 25.1 g (approx. 1.1 mol) of metallic sodium with 4N purity was also supplied to the autoclave.

[0042] 18 plates of monocrystalline gallium nitride were used as seeds; they were obtained by HVPE or by crystallization from supercritical ammonia solution oriented perpendicularly to the c-axis of the monocrystal with a diameter of approx. 38 mm (1.5 inch) and thickness of about 1,000 μm each. The seeds were placed in the crystallization zone of the autoclave.

[0043] Next, the autoclave was filled with ammonia (5N) in the amount of 230 g (approx. 13.6 mol), closed and placed in a set of heaters.

[0044] The dissolution zone was heated (at the rate of approx. 0.5° C./min) up to 450° C. At that time the crystallization zone was not heated. After the predetermined temperature of 450° C. was reached in the dissolution zone (i.e. after approx. 15 hours from the beginning of the process), the temperature in the crystallization zone was about 170° C. Such a temperature distribution was maintained in the autoclave for 4 days. At that time the source material, i.e. polycrystalline GaN, was partially supplied to the solution. Next, the temperature in the crystallization zone was raised (at the rate of approx. 0.1° C./min) up to 550° C. while the temperature in the dissolution zone stayed unchanged. The pressure inside the autoclave was approx. 410 MPa. Such a temperature distribution resulted in convection between the zones in the autoclave and consequently—in chemical transport of gallium nitride from the dissolution zone (the upper one) to the crystallization zone (the bottom one), where it is deposited on the seeds. The distribution of temperature (i.e. 450° C. in the dissolution zone and 550° C. in the crystallization zone) was maintained for the next 56 days (until the end of the process).

[0045] As a result of the process the source material (i.e. polycrystalline GaN) was partially dissolved in the dissolution zone and monocrystalline gallium nitride grew on the seeds—(on every seed) about 1.75 mm (measured in the direction of c-axis of the monocrystal). This process produced a highly resistive (semi-insulating) material with a resistivity of 3×10.sup.8Ωcm. The concentration of oxygen measured by secondary ion mass spectrometry (SIMS) amounted to 2.5×10.sup.18cm.sup.−3 and the concentration Mn—2×10.sup.20cm.sup.−3.

Example 2

Obtaining Doped GaN (Gd:NH.SUB.3.=0.001; Mn:NH.SUB.3.=0.000015; K:NH.SUB.3.=0.04)

[0046] The source material, i.e. 1.4 kg (approx. 20.2 mol) of metallic Ga containing 31.76 g of Gd (0.2 mol) and 166 mg of Mn (3 mmol), was placed in a dissolution zone of a high pressure autoclave with a capacity of 9300 cm.sup.3. 316 g (approx. 8.1 mol) of metallic potassium with 4N purity was also supplied to the autoclave.

[0047] 120 plates of monocrystalline gallium nitride were used as seeds; they were obtained by HVPE or by crystallization from supercritical ammonia solution oriented perpendicularly to the c-axis of the monocrystal with a diameter of approx. 38 mm (1.5 inch) and thickness of about 1,000 μm each. The seeds were placed in the crystallization zone of the autoclave.

[0048] Next, the autoclave was filled with ammonia (5N) in the amount of 3.44 kg (approx. 202 mol), closed and placed in a set of heaters.

[0049] The dissolution zone was heated (at the rate of approx. 0.5° C./min) up to 450° C. At that time the crystallization zone was not heated. After the predetermined temperature of 450° C. was reached in the dissolution zone (i.e. after approx. 15 hours from the beginning of the process), the temperature in the crystallization zone was about 170° C. Such a temperature distribution was maintained in the autoclave for 4 days. At that time gallium was partially supplied to the solution and undissolved gallium completely reacted to polycrystalline GaN. Next, the temperature in the crystallization zone was raised (at the rate of approx. 0.1° C./min) up to 550° C. while the temperature in the dissolution zone stayed unchanged. The pressure inside the autoclave was approx. 410 MPa. Such a temperature distribution resulted in convection between the zones in the autoclave and consequently—in chemical transport of gallium nitride from the dissolution zone (the upper one) to the crystallization zone (the bottom one), where it deposited on the seeds. The distribution of temperature (i.e. 450° C. in the dissolution zone and 550° C. in the crystallization zone) was maintained for the next 56 days (until the end of the process).

[0050] As a result of the process a layer of GaN was obtained (on every seed) with thickness of about 1.8 mm (measured in the direction of c-axis of the monocrystal). This process produced a highly resistive (semi-insulating) material with a resistivity of 8×10.sup.12 Ωcm. The concentration of oxygen measured by secondary ion mass spectrometry (SIMS) amounted to 1.8×10.sup.18 cm.sup.−3 and the concentration of Mn—8×10.sup.18 cm.sup.−3.

Example 3

Obtaining Doped GaN (Y:NH.SUB.3.=0.002; Mn:NH.SUB.3.=0.00005; Na:NH.SUB.3.=0.06)

[0051] The same procedure as in Example 2 except for the use of an autoclave with a capacity of 600 cm.sup.3; 94.8 g of metallic Ga (1.36 mol), 2.4 g of Y (approx. 0.27 mol), 37 mg of Mn (0.68 mmol), 18.8 g of Na (0.82 mol) were used as solid source substances.

[0052] The process resulted in obtaining (on every seed) a GaN layer with a thickness of about 1.6 mm (measured in the c-axis of the monocrystal). Highly resistive (semi-insulating) material was produced with a resistivity of 5×10.sup.11 Ωcm. The concentration of oxygen measured by secondary ion mass spectroscopy (SIMS) was 2.1×10.sup.18 cm.sup.−3, the concentration of Mn—4×10.sup.19cm.sup.−3.

Example 4

Obtaining Doped GaN (Ca:NH.SUB.3.=0.01; Fe:NH.SUB.3.=0.004; K:NH.SUB.3.=0.04)

[0053] The same procedure as in Example 1 except that the following were used as solid source substances: 113.8 g of polycrystalline GaN (1.36 mol), 5.4 g of Ca (approx. 137 mmol), 3.06 g of Fe (54.7 mmol), 21.4 g of K (0.55 mol).

[0054] The process resulted in obtaining (on every seed) a GaN layer with a thickness of about 1.6 mm (measured in the c-axis of the monocrystal). Highly resistive (semi-insulating) material was produced with a resistivity of 6×10.sup.9 Ωcm. The concentration of oxygen measured by secondary ion mass spectroscopy (SIMS) was 1.8×10.sup.18 cm.sup.−3, the concentration of Fe—8×10.sup.18cm.sup.−3.

Example 5

Obtaining Doped GaN (Gd:NH.SUB.3.=0.001; Fe:NH.SUB.3.=0.0005; Na:NH.SUB.3.=0.1)

[0055] The same procedure as in Example 1 except that the following were used as solid source substances: 113.8 g of polycrystalline GaN (1.36 mol), 2.15 g of Gd (approx. 13.4 mmol), 0.38 g of Fe (6.8 mmol), 31.4 g of Na (1.4 mol).

[0056] The process resulted in obtaining (on every seed) a GaN layer with a thickness of about 1.6 mm (measured in the c-axis of the monocrystal). Highly resistive (semi-insulating) material was produced with a resistivity of 7×10.sup.10 Ωcm. The concentration of oxygen measured by secondary ion mass spectroscopy (SIMS) was 7×10.sup.17cm.sup.−3, the concentration of Fe—2×10.sup.18cm.sup.−3.

Example 6

Obtaining Doped GaN (Y:NH.SUB.3.=0.004; V:NH.SUB.3.=0.08; K:NH.SUB.3.=0.1)

[0057] The same procedure as in Example 2 except for the use of an autoclave with a capacity of 600 cm.sup.3; 94.8 g of metallic Ga (1.36 mol), 4.9 g of Y (approx. 54.7 mmol), 55.8 g of mg V (1.1 mol), 53.4 g of K (1.3 mol) were used as solid source substances.

[0058] The process resulted in obtaining (on every seed) a GaN layer with a thickness of about 1.6 mm (measured in the c-axis of the monocrystal). Highly resistive (semi-insulating) material was produced with a resistivity of 5×10.sup.6 Ωcm. The concentration of oxygen measured by secondary ion mass spectroscopy (SIMS) was 1.7×10.sup.18 cm.sup.−3, the concentration of V—5×10.sup.18cm.sup.−3.

Example 7

Obtaining Doped GaN (Ca:NH.SUB.3.=0.01; V:NH.SUB.3.=0.0075; Na:NH.SUB.3.=0.06)

[0059] The same procedure as in Example 1 except that the following were used as solid source substances: 113.8 g of polycrystalline GaN (1.36 mol), 5.4 g of Ca (approx. 137 mmol), 5.2 g of V (102 mmol), 18.9 g of Na (0.82 mol).

[0060] The process resulted in obtaining (on every seed) a GaN layer with a thickness of about 1.6 mm (measured in the c-axis of the monocrystal). Highly resistive (semi-insulating) material was produced with a resistivity of 2×10.sup.10 Ωcm. The concentration of oxygen measured by secondary ion mass spectroscopy (SIMS) was 1.5×10.sup.18 cm.sup.−3, the concentration of V—1×10.sup.18 cm.sup.−3.

Example 8

Obtaining Doped GaN (Gd:NH.SUB.3.=0.002; C:NH.SUB.3.=0.003, Na:NH.SUB.3.=0.08).

[0061] The same procedure as in Example 1 except that the following were used as solid source substances: 113.8 g of polycrystalline GaN (1.36 mol), 4.3 g of Gd (approx. 27.3 mmol), 0.5 g of C (41 mmol), 25.1 g of Na (1.1 mol).

[0062] The process resulted in obtaining (on every seed) a GaN layer with a thickness of about 1.6 mm (measured in the c-axis of the monocrystal). Highly resistive (semi-insulating) material was produced with a resistivity of 4×10.sup.8 Ωcm. The concentration of oxygen measured by secondary ion mass spectroscopy (SIMS) was 1.3×10.sup.18 cm.sup.−3, the concentration of C—3×10.sup.19cm.sup.−3.

Example 9

Obtaining Doped GaN (Ca:NH.SUB.3.=0.005; C:NH.SUB.3.=0.0004, K:NH.SUB.3.=0.1).

[0063] The same procedure as in Example 2 except for the use of an autoclave with a capacity of 600 cm.sup.3; 94.8 g of metallic Ga (1.36 mol), 2.7 g of Ca (approx. 68 mmol), 65 mg of C (5.5 mmol), 53.4 g of K (1.3 mol) were used as solid source substances.

[0064] The process resulted in obtaining (on every seed) a GaN layer with a thickness of about 1.6 mm (measured in the c-axis of the monocrystal). Highly resistive (semi-insulating) material was produced with a resistivity of 3×10.sup.11Ωcm. The concentration of oxygen measured by secondary ion mass spectroscopy (SIMS) was 2×10.sup.18 cm.sup.−3, the concentration of C—9×10.sup.18cm.sup.−3.

[0065] 13