GROUP-III NITRIDE SEMICONDUCTOR FREESTANDING SUBSTRATE AND MANUFACTURING METHOD OF THE SAME

• US 20100258812A1
• Filed: 09/10/2009
• Published: 10/14/2010
• Est. Priority Date: 04/13/2009
• Status: Active Grant

• Current Assignee: Sumitomo Chemical Company Limited
• Original Assignee: Hitachi Cable Limited (Proterial Ltd.)
• Inventors: Eri, Takeshi, Meguro, Takeshi
• Granted Patent: US 8,102,026 B2
• Time in Patent Office: Days
• US Class Current: 257/76
• CPC Class Codes: C30B 25/02 Epitaxial-layer growth
• CPC Class Codes: C30B 29/403 AIII-nitrides
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/0262 Reduction or decomposition of gaseous compounds, e.g. CVD

Abstract

To provide a group-III nitride semiconductor freestanding substrate, with carrier concentration of a peripheral part of a n-type group-III nitride semiconductor freestanding substrate set to be lower than the carrier concentration inside of the peripheral part. In this freestanding substrate, preferably value Δσ obtained by dividing a difference between a maximum value of the carrier concentration and a minimum value of the carrier concentration in a surface of the freestanding substrate by the maximum value of the carrier concentration is greater than 0.05, and the carrier concentration in any place in the surface of the freestanding substrate exceeds 5.0×10¹⁷cm⁻³.

Claims

1. A group-III nitride semiconductor freestanding substrate, with carrier concentration of a peripheral part of a n-type group-III nitride semiconductor freestanding substrate set to be lower than the carrier concentration inside of the peripheral part.

2. The group-III nitride semiconductor freestanding substrate according to claim 1, wherein value Δ

σ

obtained by dividing a difference between a maximum value of the carrier concentration and a minimum value of the carrier concentration in a surface of the freestanding substrate by the maximum value of the carrier concentration is greater than 0.05, and the carrier concentration in any place in the surface of the freestanding substrate exceeds 5.0×

10¹⁷ cm<sup>−

3</sup>.

3. The group-III nitride semiconductor freestanding substrate according to claim 2, wherein the value Δ

σ

is 0.18 or less.

4. The group-III nitride semiconductor freestanding substrate according to claim 2, wherein the value Δ

σ

is 0.13 or more and 0.18 or less.

5. The group-III nitride semiconductor freestanding substrate according to claim 1, wherein a main surface of the group-III nitride semiconductor freestanding substrate is any one of C-face, M-face, or A-face.

6. The group-III nitride semiconductor freestanding substrate according to claim 1, wherein the carrier concentration is decreased gradually toward the peripheral part from a center part of the group-III nitride semiconductor substrate.

7. The group-III nitride semiconductor freestanding substrate according to claim 1, wherein the carrier concentration is highest in an intermediate part between a center part and the peripheral part of the group-III nitride semiconductor freestanding substrate, and the carrier concentration is decreased from the intermediate part to the peripheral part.

8. The group-III nitride semiconductor freestanding substrate according to claim 1, wherein the group-III nitride semiconductor freestanding substrate is a GaN substrate.

9. The group-III nitride semiconductor freestanding substrate according to claim 1, wherein n-type dopant of the group-III nitride semiconductor freestanding substrate is Si.

10. The group-III nitride semiconductor freestanding substrate according to claim 1, wherein the group-III nitride semiconductor freestanding substrate has a thickness of 200 μ

m or more, and a diameter of 2 inch or more.

11. A manufacturing method of a group-III nitride semiconductor freestanding substrate, comprising the steps of:

growing a group-III nitride semiconductor layer on a growth surface of a base substrate, by supplying required group-III source gas, nitrogen source gas, n-type dopant gas and carrier gas, to the growth surface of the base substrate; and

manufacturing the group-III nitride semiconductor freestanding substrate from the group-III nitride semiconductor layer obtained by removing the base substrate,

wherein in the step of growing the group-III nitride semiconductor layer, flow of the group-III source gas, the nitrogen source gas, the n-type dopant gas, and the carrier gas in the vicinity of the growth surface of the base substrate is adjusted, so that a carrier concentration of a peripheral part of the group-III nitride semiconductor layer is lower than the carrier concentration inside of the peripheral part.

12. The manufacturing method of the group-III nitride semiconductor freestanding substrate according to claim 11, wherein in the step of growing the group-III nitride semiconductor layer, an outer edge part of the base substrate is held by a substrate holder, and a thickness of a part of the substrate holder protruded from the growth surface of the base substrate in a growing direction of the group-III nitride semiconductor layer is adjusted, so that the carrier concentration of the peripheral part of the group-III nitride semiconductor layer is lower than the carrier concentration inside of the peripheral part.

13. The manufacturing method of the group-III nitride semiconductor freestanding substrate according to claim 11, wherein in the step of growing the group-III nitride semiconductor layer, an outer edge part of the base substrate is held by a substrate holder, and a flow rate of purge gas flowing from a gap between an outer peripheral surface of the base substrate and an inner peripheral surface of the substrate holder is adjusted, so that the carrier concentration of the peripheral part of the group-III nitride semiconductor layer is lower than the carrier concentration inside of the peripheral part.

14. The manufacturing method of the group-III nitride semiconductor freestanding substrate according to claim 11, wherein in the step of growing the group-III nitride semiconductor layer, a flow rate of the carrier gas is adjusted, so that the carrier concentration of the peripheral part of the group-III nitride semiconductor layer is lower than the carrier concentration inside of the peripheral part.

15. The manufacturing method of the group-III nitride semiconductor freestanding substrate according to claim 11, wherein a growth of the group-III nitride semiconductor layer is performed by using a hydride vapor phase epitaxy.