GaN single crystal and method for manufacturing GaN single crystal

• US 10,301,743 B2
• Filed: 07/28/2017
• Issued: 05/28/2019
• Est. Priority Date: 02/06/2015
• Status: Active Grant

• Current Assignee: Mitsubishi Chemical Corporation (Mitsubishi Chemical Group Corp.)
• Original Assignee: Mitsubishi Chemical Corporation (Mitsubishi Chemical Group Corp.)
• Inventors: Fujisawa, Hideo, Mikawa, Yutaka, Kawabata, Shinichiro, Namita, Hideo, Mochizuki, Tae
• Primary Examiner(s): Kunemund, Robert M
• Application Number:
  US15/663,276
• Publication Number:
  US 20170327971A1
• Time in Patent Office: 669 Days
• CPC Class Codes: C30B 25/18 characterised by the substrate
• CPC Class Codes: C30B 29/38 Nitrides
• CPC Class Codes: C30B 29/406 Gallium nitride
• CPC Class Codes: C30B 7/10 by application of pressure, e.g. hydrothermal processes
• CPC Class Codes: C30B 7/105 using ammonia as solvent, i.e. ammonothermal processes
• CPC Class Codes: H01L 21/0242 Crystalline insulating materials
• CPC Class Codes: H01L 21/0254 Nitrides

Abstract

A new GaN single crystal is provided. A GaN single crystal according to the present embodiment comprises a gallium polar surface which is a main surface on one side and a nitrogen polar surface which is a main surface on the opposite side,

• • wherein on the gallium polar surface is found at least one square area, an outer periphery of which is constituted by four sides each with a length of 2 mm or more, and, when the at least one square are is divided into a plurality of sub-areas each of which is a square of 100 μm×100 μm, pit-free areas account for 80% or more of the sub-areas.

Claims

1. A method for producing a GaN single crystal, comprising the steps of:

(S1) preparing a seed comprising a nitrogen polar surface of GaN;

(S2) forming a pattern mask on the nitrogen polar surface of the prepared seed; and

(S3) forming a GaN crystal layer on the nitrogen polar surface on which the pattern mask is formed, by an ammonothermal method,

wherein in the step (S3) mineralizers are used, said mineralizers comprising ammonium fluoride and an ammonium halide selected from the group consisting of ammonium chloride, ammonium bromide and ammonium iodide,

wherein the pattern mask is a rhomboid grid type pattern mask which comprises a plurality of first linear openings extending along a first extending direction and having a constant pitch therebetween and a plurality of second linear openings extending along a second extending direction and having a constant pitch therebetween, and

wherein in the step (S3), GaN crystals grow laterally above the pattern mask, and coalesce with each other to form the GaN crystal layer while forming voids between the pattern mask and the GaN crystal layer.

2. The production method according to claim 1,

wherein the pitch between the first linear openings is 3 mm or more and 20 mm or less.

3. The production method according to claim 2,

wherein the pitch between the second linear openings is 3 mm or more and 20 mm or less.

4. The production method according to claim 1,

wherein, when an extending direction of one of intersection lines between the nitrogen polar surface and the M-planes of the seed is selected as a reference direction, an angle formed between the first extending direction and the reference direction is within a range of 12°

±

5°

.

5. The production method according to claim 4,

wherein an angle formed between the second extending direction and the reference direction is within a range of 72°

±

5°

.

6. The production method according to claim 1,

wherein an angle formed between the first extending direction and the second extending direction is 60°

.

7. The production method according to claim 1,

wherein the size of each of the voids in the c-axis direction is 1 mm or more.

10. The production method according to claim 1,

wherein the ammonium halide is ammonium iodide.

8. A method for producing a GaN single crystal, comprising the steps of:

(S1) preparing a seed comprising a nitrogen polar surface of GaN;

(S2) forming a pattern mask on the nitrogen polar surface of the prepared seed; and

(S3) forming a GaN crystal layer on the nitrogen polar surface on which the pattern mask is formed, by an ammonothermal method,

wherein in the step (S3) mineralizers are used, said mineralizers comprising ammonium fluoride and an ammonium halide selected from the group consisting of ammonium chloride, ammonium bromide and ammonium iodide,

wherein the pattern mask is a hexagonal grid type pattern mask which comprises a plurality of first linear openings extending along a first extending direction and having a first constant pitch therebetween, a plurality of second linear openings extending along a second extending direction and having a second constant pitch therebetween, and a plurality of third linear openings extending along a third extending direction and having a third constant pitch therebetween, and

wherein in the step (S3), GaN crystals grow laterally above the pattern mask, and coalesce with each other to form the GaN crystal layer while forming voids between the pattern mask and the GaN crystal layer.

9. The production method according to claim 8,

wherein the size of each of the voids in the c-axis direction is 1 mm or more.

11. The production method according to claim 8,

wherein the ammonium halide is ammonium iodide.

12. The production method according to claim 8,

wherein the first constant pitch, the second constant pitch and the third constant pitch are all 4 mm or more and 20 mm or less.

13. The production method according to claim 8,

wherein, when an extending direction of one of intersection lines between the nitrogen polar surface and the M-planes of the seed is selected as a reference direction, an angle formed between the first extending direction and the reference direction is within a range of 12°

±

5°

.

14. The production method according to claim 13,

wherein an angle formed between the second extending direction and the reference direction is within a range of 72°

±

5°

.

15. The production method according to claim 14,

wherein an angle formed between the third extending direction and the reference direction is within a range of 132°

±

5°

.