NITRIDE SEMICONDUCTOR DEVICE, NITRIDE SEMICONDUCTOR WAFER, AND METHOD FOR FORMING NITRIDE SEMICONDUCTOR LAYER

• US 20140138699A1
• Filed: 02/28/2013
• Published: 05/22/2014
• 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
• Granted Patent: US 9,054,036 B2
• Time in Patent Office: Days
• US Class Current: 257/76
• 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 including

an AlGaN layer of Al_xGa_1-xN (0<

x≦

1),

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

10¹⁹/cm³ and not more than 4×

10²⁰/cm³,

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

a second Si-containing layer provided on the first GaN layer, the second Si-containing layer containing Si, and

a second GaN layer provided on the second Si-containing layer; and

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

2. The device according to claim 1, wherein the first GaN layer has a plurality of first dislocations communicating with the oblique surface inside the protrusion, and a number of the dislocations inside the second GaN layer continuous with the first dislocations via the second Si-containing layer is less than a number of the plurality of first dislocations.

3. The device according to claim 1, wherein

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

the first GaN layer has

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

a plurality of second dislocations communicating with the top surface inside the protrusion,

the second GaN layer has a plurality of third dislocations,

a portion of the plurality of 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

an upper surface of the first Si-containing layer includes a first region and a second region,

the first GaN layer is provided on the first region, and

a portion of the second Si-containing layer contacts the first Si-containing layer in the second region.

6. The device according to claim 1, wherein a Si concentration profile of the stacked body has

a first portion having a first concentration, a Si concentration of the first concentration being not less than 7×

10¹⁹/cm³ and not more than 4×

10²⁰/cm³,

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

a third portion provided between the first portion and the second portion, the third portion having a third concentration, a Si concentration of the third concentration being between the first concentration and the second concentration,

a fourth portion provided between the third portion and the second portion, the fourth portion having a fourth concentration, a Si concentration of the fourth concentration being between the third concentration and the second concentration,

a fifth portion provided between the first portion and the third portion, a Si concentration change per thickness of the fifth portion being higher than a Si concentration change per thickness of the third portion,

a sixth portion provided between the third portion and the fourth portion, a Si concentration change per thickness of the sixth portion being higher than the Si concentration change per thickness of the third portion and higher than a Si concentration change per thickness of the fourth portion, and

a seventh portion provided between the fourth portion and the second portion, a Si concentration change per thickness of the seventh portion being higher than the Si concentration change per thickness of the fourth portion and higher than a Si concentration change per thickness of the second portion.

7. The device according to claim 6, wherein the third concentration of the third portion is not less than 3×

10¹⁸/cm³ and not more than 5×

10¹⁹/cm³.

8. The device according to claim 6, wherein

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

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

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

9. The device according to claim 1, further comprising a buffer layer including the nitride semiconductor,

the stacked body being provided on the buffer layer.

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

the stacked intermediate layer including:

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.

11. The device according to claim 9, further comprising a substrate,

the buffer layer being disposed between the substrate and the stacked body.

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

13. A nitride semiconductor wafer, comprising:

a substrate;

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

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

an AlGaN layer of Al_xGa_1-xN (0<

x≦

1);

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

10¹⁹/cm³ and not more than 4×

10²⁰/cm³;

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

a second Si-containing layer provided on the first GaN layer, the second Si-containing layer containing Si; and

a second GaN layer provided on the second Si-containing layer.

14. The wafer according to claim 13, wherein the first GaN layer has a plurality of first dislocations communicating with the oblique surface inside the protrusion, and a number of dislocations inside the second GaN layer continuous with the first dislocations via the second Si-containing layer is less than a number of the plurality of first dislocations.

15. The wafer according to claim 13, wherein

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

the first GaN layer has

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

a plurality of second dislocations communicating with the top surface inside the protrusion,

the second GaN layer has a plurality of third dislocations,

a portion of the plurality of 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.

16. The wafer according to claim 13, wherein a height of the protrusion is not less than 100 nm and not more than 1000 nm.

17. The wafer according to claim 13, wherein

an upper surface of the first Si-containing layer includes a first region and a second region,

the first GaN layer is provided on the first region, and

a portion of the second Si-containing layer contacts the first Si-containing layer in the second region.

18. The wafer according to claim 13, further comprising a stacked intermediate layer provided between the buffer layer and the stacked body,

the stacked intermediate layer including:

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.

19. The wafer according to claim 13, wherein the substrate is a silicon substrate.

20. 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 containing Si at a concentration not less than 7×

10¹⁹/cm³ and not more than 4×

10²⁰/cm³;

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

forming a second Si-containing layer containing Si on the first GaN layer; and

forming a second GaN layer on the second Si-containing layer.