Nitride Semiconductor Light-Emitting Device and Nitride Semiconductor Light-Emitting Device Fabrication Method

• US 20100032644A1
• Filed: 03/28/2008
• Published: 02/11/2010
• Est. Priority Date: 04/06/2007
• Status: Abandoned Application

• Current Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Original Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Inventors: Kasai, Hitoshi, Kyono, Takashi, Akita, Katsushi, Ishibashi, Keiji
• Application Number:
  US12/307,586
• Publication Number:
  US 20100032644A1
• Time in Patent Office: Days
• US Class Current: 257/13
• CPC Class Codes: H01L 21/0237 Materials
• CPC Class Codes: H01L 21/02389 Nitrides
• CPC Class Codes: H01L 21/02433 Crystal orientation
• CPC Class Codes: H01L 21/02458 Nitrides
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/0262 Reduction or decomposition of gaseous compounds, e.g. CVD
• CPC Class Codes: H01L 33/06 within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: H01L 33/16 with a particular crystal structure or orientation, e.g. polycrystalline, amorphous or porous
• CPC Class Codes: H01L 33/32 containing nitrogen

Abstract

An active layer (17) is provided so as to emit light having an emission wavelength in the 440 nm to 550 nm band. A first-conductivity-type gallium nitride semiconductor region (13), the active layer (17), and a second-conductivity-type gallium nitride semiconductor region (15) are arranged along a predetermined axis (Ax). The active layer (17) includes a well layer composed of hexagonal In_xGa_1-xN (0.16≦x≦0.4, x: strained composition), with the indium fraction x represented by the strained composition. The m-plane of the hexagonal In_xGa_1-xN is oriented along the predetermined axis (Ax). The well-layer thickness is between greater than 3 nm and less than or equal to 20 nm. Having the well-layer thickness be over 3 nm makes it possible to fabricate light-emitting devices having an emission wavelength of over 440 nm.

Claims

1. A nitride semiconductor light-emitting device, furnished with:

a gallium nitride semiconductor region of a first conductivity type;

a gallium nitride semiconductor region of a second conductivity type; and

an active layer provided between the first-conductivity-type gallium nitride semiconductor region and the second-conductivity-type gallium nitride semiconductor region, the active layer being provided so as to emit light of wavelength in the band from 440 nm to 550 nm inclusive;

characterized in that

the active layer includes a well layer composed of hexagonal In_xGa_1-xN (0.16≦

x≦

0.4, indium fraction x;

strained composition),

the well-layer thickness D is greater than 3 nm,

the well-layer thickness D is 20 nm or less,

the thickness D by the indium fraction x lies in the relationship x≧

−

0.16×

D+0.88,

the first-conductivity-type gallium nitride semiconductor region, the active layer, and the second-conductivity-type gallium nitride semiconductor region are arranged along a predetermined-axis, and

the m-plane of the hexagonal In_xGa_1-xN is oriented along the predetermined axis.

2. The nitride semiconductor light-emitting device set forth in claim 1, characterized in that the active layer includes a barrier layer composed of hexagonal In_yGa_1-yN (0≦

y≦

0.05, y;

strained composition).

3. The nitride semiconductor light-emitting device set forth in claim 1 or claim 2, further including a substrate composed of hexagonal Al_zGa_1-zN semiconductor (0≦

z≦

1), and characterized in that

the first-conductivity-type gallium nitride semiconductor region, the active layer, and the second-conductivity-type gallium nitride semiconductor region are carried on the principal face of the substrate.

4. The nitride semiconductor light-emitting device set forth in claim 3, characterized in that the substrate principal face is misoriented at a given off-axis angle (−

2°

≦

θ

≦

+2°

) from the m-plane.

5. The nitride semiconductor light-emitting device set forth in claim 3, characterized in that:

threading dislocations in the substrate extend in the c-axis direction; and

the density of threading dislocations crossing the substrate'"'"'s c-plane is 1×

10⁷ cm<sup>−

2</sup> or less.

6. The nitride semiconductor light-emitting device set forth in claim 3, characterized in that:

the substrate includes a first region in which the density of threading dislocations extending in the c-axis direction is greater than a first threading dislocation density, and a second region in which the density of threading dislocations extending in the c-axis direction is less than the first threading dislocation density; and

the first and second regions appear on the substrate principal face.

7. The nitride semiconductor light-emitting device set forth in claim 6, characterized in that the threading dislocation density in the second region is less than 1×

10⁷ cm<sup>−

2</sup>.

8. A nitride semiconductor light-emitting device fabricating method, furnished with:

a step of preparing a substrate composed of hexagonal Al_zGa_1-zN semiconductor (0≦

z≦

1);

a step of forming a gallium nitride semiconductor film of a first conductivity type onto the principal face of the substrate;

a step of forming onto the first-conductivity-type gallium nitride semiconductor film an active layer such as to emit light of wavelength in the band from 440 nm to 550 nm inclusive; and

a step of forming onto the active layer a gallium nitride semiconductor film of a second conductivity type;

characterized in that

the first-conductivity-type gallium nitride semiconductor film, the active layer, and the second-conductivity-type gallium nitride semiconductor film are arranged on the substrate principal face along a predetermined axis,

in the active-layer forming step, a first semiconductor layer, composed of hexagonal In_xGa_1-xN (0.16≦

x≦

0.4, x;

strained composition), having a first gallium fraction is grown at a first temperature, and

in the active layer forming step, a second semiconductor layer, composed of hexagonal In_yGa_1-yN (0≦

y≦

0.05, y<

x, y;

strained composition), having a second gallium fraction is grown at a second temperature;

the first gallium fraction is lower than the second gallium fraction;

the first temperature is lower than the second temperature;

the difference between the first temperature and the second temperature is 95 degrees or more; and

the m-plane of the hexagonal In_xGa_1-xN is oriented along the predetermined axis.

9. The method set forth in claim 8, characterized in that from hexagonal Al_zGa_1-zN semiconductor crystal (0≦

z≦

1) grown c-axis oriented, the substrate is sliced so as to intersect the m-axis, and the substrate principal face is polish-processed and stretches paralleling a plane that intersects the m-axis.

10. The method set forth in claim 8 or claim 9, characterized in that:

the substrate includes a plurality of first regions in which the density of threading dislocations extending in the c-axis direction is greater than a first threading dislocation density, and a plurality of second regions in which the density of threading dislocations extending in the c-axis direction is less than the first threading dislocation density;

the first and second regions are arranged in alternation; and

the first and second regions appear on the substrate principal face.

11. The method set forth in claim 10, characterized in that the threading dislocation density in the second regions is less than 1×

10⁷ cm<sup>−

2</sup>.

12. The method set forth in claim 8, characterized in that the substrate principal face is misoriented at an off-axis angle (−

2°

≦

θ

≦

+2°

) from the m-plane.

13. A method as set forth in claim 8, characterized in being further furnished with a step of, in advance of the formation of the first-conductivity-type gallium nitride semiconductor film, heat-treating the substrate while supplying thereto a gas containing ammonia and hydrogen.