Group-iii element nitride substrate and method of producing group-iii element nitride substrate

Patent metadata

Field	Value
Publication number	US-2025389051-A1
Application number	US-202519317370-A
Country	US
Kind code	A1
Filing date	Sep 3, 2025
Priority date	Mar 3, 2023
Publication date	Dec 25, 2025
Grant date	—

Abstract

A Group-III element nitride substrate includes a first main surface and a second main surface facing each other. The Group-III element nitride substrate has a first direction, which extends in a surface direction, and in which a carrier concentration or a defect density is decreased from a first end portion side to a second end portion side, in a substrate surface of the Group-III element nitride substrate.

First claim

What is claimed is:

1 . A Group-III element nitride substrate, comprising a first main surface and a second main surface facing each other,
wherein the Group-III element nitride substrate has a first direction, which extends in a surface direction, and in which a carrier concentration is decreased from a first end portion side to a second end portion side, in a substrate surface of the Group-III element nitride substrate.

2 . The Group-III element nitride substrate according to claim 1 , wherein the carrier concentration is monotonously decreased from the first end portion side to the second end portion side in the first direction.

3 . The Group-III element nitride substrate according to claim 1 , wherein the carrier concentration on a line along the first direction has a distribution of 7% or more.

4 . The Group-III element nitride substrate according to claim 3 ,
wherein the Group-III element nitride substrate has a second direction, which extends in the surface direction, and which is perpendicular to the first direction, in the substrate surface, and wherein the carrier concentration on a line along the second direction has a distribution of less than 7%.

5 . The Group-III element nitride substrate according to claim 1 , wherein the carrier concentration on a line along the first direction has a distribution of 10% or more.

6 . The Group-III element nitride substrate according to claim 5 ,
wherein the Group-III element nitride substrate has a second direction, which extends in the surface direction, and which is perpendicular to the first direction, in the substrate surface, and wherein the carrier concentration on a line along the second direction has a distribution of less than 10%.

7 . A Group-III element nitride substrate, comprising a first main surface and a second main surface facing each other,
wherein the Group-III element nitride substrate has a first direction, which extends in a surface direction, and in which a defect density is decreased from a first end portion side to a second end portion side, in a substrate surface of the Group-III element nitride substrate.

8 . The Group-III element nitride substrate according to claim 7 , wherein the defect density is monotonously decreased from the first end portion side to the second end portion side in the first direction.

9 . The Group-III element nitride substrate according to claim 7 , wherein the defect density on a line along the first direction has a distribution of 30% or more.

10 . The Group-III element nitride substrate according to claim 9 ,
wherein the Group-III element nitride substrate has a second direction, which extends in the surface direction, and which is perpendicular to the first direction, in the substrate surface, and wherein the defect density on a line along the second direction has a distribution of less than 30%.

11 . The Group-III element nitride substrate according to claim 7 , wherein the defect density on a line along the first direction has a distribution of 50% or more.

12 . The Group-III element nitride substrate according to claim 11 ,
wherein the Group-III element nitride substrate has a second direction, which extends in the surface direction, and which is perpendicular to the first direction, in the substrate surface, and wherein the defect density on a line along the second direction has a distribution of less than 50%.

13 . The Group-III element nitride substrate according to claim 1 , wherein the first direction substantially corresponds to a direction in which a c-axis of a Group-III element nitride crystal is tilted with respect to a normal of the main surface in plan view.

14 . The Group-III element nitride substrate according to claim 13 , wherein an angle of the tilt is more than 0° and less than 1°.

15 . The Group-III element nitride substrate according to claim 1 , wherein the Group-III element nitride substrate is a freestanding substrate of a Group-III element nitride crystal.

16 . A method of producing the Group-III element nitride substrate of claim 1 , the method comprising:
preparing a seed crystal substrate including: a base substrate including an upper surface and a lower surface facing each other; and a seed crystal film to be formed on the upper surface of the base substrate; growing a Group-III element nitride crystal on the seed crystal film of the seed crystal substrate by a flux method; and removing the base substrate from the Group-III element nitride crystal, wherein the growing the Group-III element nitride crystal by the flux method is performed by arranging the seed crystal substrate on a mounting table that is rotated about a vertical axis, wherein a center of the seed crystal substrate is spaced apart from a rotation axis of the mounting table, and wherein the seed crystal substrate is arranged so that an angle formed by an off-angle direction of the seed crystal film of the seed crystal substrate and a normal of the rotation axis of the mounting table that passes through the center of the seed crystal substrate is substantially 0° in plan view.

17 . The production method according to claim 16 , wherein the base substrate contains a material different in composition from the Group-III element nitride crystal.

18 . The Group-III element nitride substrate according to claim 7 , wherein the first direction substantially corresponds to a direction in which a c-axis of a Group-III element nitride crystal is tilted with respect to a normal of the main surface in plan view.

19 . The Group-III element nitride substrate according to claim 7 , wherein the Group-III element nitride substrate is a freestanding substrate of a Group-III element nitride crystal.

20 . A method of producing the Group-III element nitride substrate of claim 7 , the method comprising:
preparing crystal substrate including: a base substrate including an upper surface and a lower surface facing each other; and a seed crystal film to be formed on the upper surface of the base substrate; growing a Group-III element nitride crystal on the seed crystal film of the seed crystal substrate by a flux method; and removing the base substrate from the Group-III element nitride crystal, wherein the growing the Group-III element nitride crystal by the flux method is performed by arranging the seed crystal substrate on a mounting table that is rotated about a vertical axis, wherein a center of the seed crystal substrate is spaced apart from a rotation axis of the mounting table, and wherein the seed crystal substrate is arranged so that an angle formed by an off-angle direction of the seed crystal film of the seed crystal substrate and a normal of the rotation axis of the mounting table that passes through the center of the seed crystal substrate is substantially 0° in plan view.

Assignees

• Ngk Insulators Ltd

Inventors

• Kuraoka Yoshitaka
• HIRAIWA Kei
• Nonaka Kentaro

Classifications

• C30B19/066

  Injection or centrifugal force system · CPC title

• C30B9/12

  Salt solvents, e.g. flux growth · CPC title

• C30B33/00

  After-treatment of single crystals or homogeneous polycrystalline material with defined structure (C30B31/00 takes precedence) · CPC title

• C30B19/02

  using molten solvents, e.g. flux · CPC title

• C30B29/406 Primary

  Gallium nitride · CPC title