Nitride semiconductor device, nitride semiconductor wafer, and method for forming nitride semiconductor layer

• US 9,054,036 B2
• Filed: 02/28/2013
• Issued: 06/09/2015
• Est. Priority Date: 11/21/2012
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Hikosaka, Toshiki, Harada, Yoshiyuki, Yoshida, Hisashi, Sugiyama, Naoharu, Nunoue, Shinya
• Primary Examiner(s): Li, Meiya
• Assistant Examiner(s): Albrecht, Peter M
• Application Number:
  US13/780,456
• Publication Number:
  US 20140138699A1
• Time in Patent Office: 831 Days
• Field of Search: 257101-103, 257/190, 257/618, 257/623, 257/E21.119, 257/E21.135, 257/E33.028, 257/E33.034
• US Class Current: 1/1
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 29/2003 Nitride compounds
• CPC Class Codes: H01L 29/205 in different semiconductor regions , e.g. heterojunctions
• CPC Class Codes: H01L 29/267 in different semiconductor regions , e.g. heterojunctions H01L29/263 takes precedence
• CPC Class Codes: H01L 33/32 containing nitrogen

Abstract

According to one embodiment, a nitride semiconductor device includes a stacked body and a functional layer. The stacked body includes an AlGaN layer of Al_xGa_1-xN (0<x≦1), a first Si-containing layer, a first GaN layer, a second Si-containing layer, and a second GaN layer. The first Si-containing layer contacts an upper surface of the AlGaN layer. The first Si-containing layer contains Si at a concentration not less than 7×10¹⁹/cm³ and not more than 4×10²⁰/cm³. The first GaN layer is provided on the first Si-containing layer. The first GaN layer includes a protrusion having an oblique surface tilted with respect to the upper surface. The second Si-containing layer is provided on the first GaN layer. The second Si-containing layer contains Si. The second GaN layer is provided on the second Si-containing layer. The functional layer is provided on the stacked body. The functional layer includes a nitride semiconductor.

Claims

1. A nitride semiconductor device, comprising:

a stacked body comprising

an AlGaN layer of Al_xGa_1-xN (0<

x≦

1) having a first upper surface,

a first Si-containing layer contacting the first upper surface, the first Si-containing layer comprising Si at a concentration not less than 7×

10¹⁹/cm³ and not more than 4×

10²⁰/cm³, the first Si-containing layer having a second upper surface, the second upper surface including a first region and a second region,

a first GaN layer provided on the first region, the first GaN layer including a protrusion having an oblique surface tilted with respect to the first upper surface,

a second Si-containing layer provided on the first GaN layer, the second Si-containing layer comprising Si, a portion of the second Si-containing layer physically contacting the second region, and

a second GaN layer provided on the second Si-containing layer, the second GaN layer physically contacting the portion of the second Si-containing layer; and

a functional layer provided on the stacked body, the functional layer including a nitride semiconductor,

wherein each of the first Si-containing layer and the second Si-containing layer comprises SiN.

2. The device according to claim 1, wherein

the first GaN layer comprises a plurality of first dislocations communicating with the oblique surface,

the second GaN layer comprises a plurality of third dislocations,

at least one of the third dislocations is continuous with the first dislocations via the second Si-containing layer, and

a number of the third dislocations continuous with the first dislocations is less than a number of the first dislocations.

3. The device according to claim 1, wherein

the protrusion of the first GaN layer further comprises a top surface parallel to the first upper surface,

the first GaN layer comprises

a plurality of first dislocations communicating with the oblique surface, and

a plurality of second dislocations communicating with the top surface of the first GaN layer,

the second GaN layer comprises a plurality of third dislocations,

at least one of the third dislocations is continuous with the second dislocations, and

a ratio of a number of the third dislocations continuous with the first dislocations to a number of the plurality of first dislocations is lower than a ratio of a number of the third dislocations continuous with the second dislocations to a number of the second dislocations.

4. The device according to claim 1, wherein a height of the protrusion is not less than 100 nm and not more than 1000 nm.

5. The device according to claim 1, wherein the stacked body comprises:

a first portion having a first Si concentration not less than 7×

10¹⁹/cm³ and not more than 4×

10²⁰/cm³,

a second portion having a second Si concentration lower than the first Si concentration,

a third portion provided between the first portion and the second portion, the third portion having a third Si concentration, wherein the third Si concentration is lower than the first Si concentration and higher than the second Si concentration,

a fourth portion provided between the third portion and the second portion, the fourth portion having a fourth Si concentration, wherein the fourth Si concentration is lower than the third Si concentration and higher than the second Si concentration,

a fifth portion provided between the first portion and the third portion, wherein a Si concentration of the fifth portion changes along a thickness of the fifth portion with a rate higher than a change of Si concentration along a thickness of the third portion,

a sixth portion provided between the third portion and the fourth portion, wherein a Si concentration of the sixth portion changes along a thickness of the sixth portion with a rate higher than the change of Si concentration along the thickness of the third portion and higher than a change of Si concentration along a thickness of the fourth portion, and

a seventh portion provided between the fourth portion and the second portion, wherein a Si concentration of the seventh portion changes along a thickness of the seventh portion with a rate higher than the change of Si concentration along the thickness of the fourth portion and higher than a change of Si concentration along a thickness of the second portion.

6. The device according to claim 5, wherein the third Si concentration is not less than 3×

10¹⁸/cm³ and not more than 5×

10¹⁹/cm³.

7. The device according to claim 5, wherein

a thickness of the first portion is not less than 1 nm and not more than 200 nm,

the thickness of the third portion is not less than 100 nm and not more than 1000 nm, and

the thickness of the fourth portion is not less than 300 nm and not more than 2500 nm.

8. The device according to claim 1, further comprising a buffer layer comprising a second nitride semiconductor, wherein

the stacked body is provided on the buffer layer.

9. The device according to claim 8, further comprising a stacked intermediate layer provided between the buffer layer and the stacked body, wherein the stacked intermediate layer comprises:

a GaN intermediate layer;

an AlN intermediate layer provided on the GaN intermediate layer; and

an AlGaN intermediate layer provided on the AlN intermediate layer.

10. The device according to claim 8, further comprising a substrate, wherein the buffer layer is disposed between the substrate and the stacked body.

11. The device according to claim 10, wherein the substrate is a silicon substrate.

12. A nitride semiconductor wafer, comprising:

a substrate;

buffer layer provided on the substrate, the buffer layer comprising a nitride semiconductor; and

a stacked body provided on the buffer layer, the stacked body comprising;

an AlGaN layer of Al_xGa_1-xN (0<

x≦

1) having a first upper surface;

a first Si-containing layer contacting the first upper surface, the first Si-containing layer comprising Si at a concentration not less than 7×

10¹⁹/cm³ and not more than 4×

10²⁰/cm³, the first Si-containing layer having a second upper surface, the second upper surface including a first region and a second region;

a first GaN layer provided on the first region, the first GaN layer including a protrusion having an oblique surface tilted with respect to the first upper surface;

a second Si-containing layer provided on the first GaN layer, the second Si-containing layer comprising Si, a portion of the second Si-containing layer physically contacting the second region; and

a second GaN layer provided on the second Si-containing layer, the second GaN layer physically contacting the portion of the second Si-containing layer,

wherein each of the first Si-containing layer and the second Si-containing layer comprises SiN.

13. The wafer according to claim 12, wherein

the first GaN layer comprises a plurality of first dislocations communicating with the oblique surface,

the second GaN layer has a plurality of third dislocations,

at least one of the third dislocations is continuous with the first dislocations via the second Si-containing layer, and

a number of the third dislocations continuous with the first dislocations is less than a number of the first dislocations.

14. The wafer according to claim 12, wherein

the protrusion of the first GaN layer further comprises a top surface parallel to the first upper surface,

the first GaN layer comprises

a plurality of first dislocations communicating with the oblique surface, and

a plurality of second dislocations communicating with the top surface of the first GaN layer,

the second GaN layer comprises a plurality of third dislocations,

at least one of the third dislocations is continuous with the second dislocations, and

a ratio of a number of the third dislocations continuous with the first dislocations to a number of the plurality of first dislocations is lower than a ratio of a number of the third dislocations continuous with the second dislocations to a number of the second dislocations.

15. The wafer according to claim 12, wherein a height of the protrusion is not less than 100 nm and not more than 1000 nm.

16. The wafer according to claim 12, further comprising a stacked intermediate layer provided between the buffer layer and the stacked body, wherein the stacked intermediate layer comprises:

a GaN intermediate layer;

an AlN intermediate layer provided on the GaN intermediate layer; and

an AlGaN intermediate layer provided on the AlN intermediate layer.

17. The wafer according to claim 12, wherein the substrate is a silicon substrate.

18. A method for forming a nitride semiconductor layer, comprising:

forming an AlGaN layer of Al_xGa_1-xN (0<

x≦

1) on a buffer layer provided on a substrate, the buffer layer including a nitride semiconductor;

forming a first Si-containing layer contacting an upper surface of the AlGaN layer, the first Si-containing layer comprising Si at a concentration not less than 7×

10¹⁹/cm³ and not more than 4×

10²⁰/cm³, the first Si-containing layer having a second upper surface, the second upper surface including a first region and a second region;

forming a first GaN layer on the first region of the first Si-containing layer, the first GaN layer including a protrusion having an oblique surface tilted with respect to the upper surface of the AlGaN layer;

forming a second Si-containing layer comprising Si on the first GaN layer, a portion of the second Si-containing layer physically contacting the second region; and

forming a second GaN layer on the second Si-containing layer, the second GaN layer physically contacting the portion of the second Si-containing layer,

wherein each of the first Si-containing layer and the second Si-containing layer comprises SiN.