Semiconductor light-emitting device and method for fabricating the same

• US 20050161696A1
• Filed: 01/19/2005
• Published: 07/28/2005
• Est. Priority Date: 01/28/2004
• Status: Abandoned Application

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Yuri, Masaaki
• Application Number:
  US11/037,188
• Publication Number:
  US 20050161696A1
• Time in Patent Office: Days
• US Class Current: 257/103
• CPC Class Codes: H01L 33/16 with a particular crystal structure or orientation, e.g. polycrystalline, amorphous or porous
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers

Abstract

In a semiconductor light-emitting device formed by stacking a plurality of semiconductor layers including an active layer, at least a portion of a semiconductor layer of the plurality of semiconductor layers is made porous. The semiconductor layer made porous has a surface serving as a light-extraction surface for extracting light emitted from the active layer.

Claims

1. A semiconductor light-emitting device which is formed by stacking a plurality of semiconductor layers including an active layer,

wherein at least a portion of a semiconductor layer of the plurality of semiconductor layers is made porous, the semiconductor layer having a surface serving as a light-extraction surface for extracting light emitted from the active layer.

2. The device of claim 1,

wherein air gaps in the porous region of the semiconductor layer have irregularities in their bottom levels.

3. The device of claim 1,

wherein the porous region of the semiconductor layer has a plurality of remaining semiconductor portions whose tops form irregularities as a whole.

4. The device of claim 1,

wherein the plurality of semiconductor layers include another semiconductor layer not made porous, provided between the active layer and the semiconductor layer, and serving as a current diffusion layer, and

an electrode is provided on a non-porous region of the semiconductor layer.

5. The device of claim 4,

wherein the current diffusion layer has at least one heterointerface.

6. The device of claim 1,

wherein an optical absorption edge of the porous region of the semiconductor layer has a shorter wavelength than that of the non-porous region of the semiconductor layer.

7. The device of claim 1,

wherein the wavelength of the optical absorption edge of the porous region of the semiconductor layer is shorter than the center wavelength of light emitted from the active layer.

8. The device of claim 1,

wherein the distance between adjacent ones of the air gaps in the porous region of the semiconductor layer is 20 nm or smaller.

9. The device of claim 1,

wherein the effective refractive index of the porous region of the semiconductor layer decreases as the distance from the active layer is increased.

10. The device of claim 1,

wherein the ratio of air gaps per unit volume of the porous region of the semiconductor layer rises as the distance from the active layer is increased.

11. The device of claim 1,

wherein the band gap energy of the semiconductor layer stepwise or continuously decreases as the distance from the active layer is increased.

12. The device of claim 1,

wherein portions of the semiconductor surface contacting with the air gaps in the porous region of the semiconductor layer are oxidized.

13. The device of claim 1,

wherein the surface side of the porous region of the semiconductor layer is covered with a protection film.

14. The device of claim 13,

wherein the protection film is made of SiO₂, Al₂O₃, SiN, TiO₂, ZrO₂, Nb₂O₅, Ta₂O₅, or Ga₂O₃.

15. The device of claim 1,

wherein the surface side of the porous region of the semiconductor layer is covered with a transparent electrode.

16. The device of claim 1,

wherein the semiconductor layer is an n-type semiconductor layer.

17. The device of claim 1,

wherein the plurality of semiconductor layers are formed on a substrate, and

a reflection film made of metal or a multilayer dielectric structure is formed on one of principal surfaces of the substrate on which the plurality of semiconductor layers are not formed.

18. The device of claim 1,

wherein a reflection film made of metal or a multilayer dielectric structure is formed on a surface of a still another semiconductor layer of the plurality of semiconductor layers, the surface of the still another semiconductor layer being the opposite surface to the light-extraction surface.

19. The device of claim 1,

wherein each of the plurality of semiconductor layers is made of nitride-based compound semiconductor represented by B_xAl_yIn_zGa_1-x-y-zN (0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, 0≦

x+y+≦

1).

20. The device of claim 19,

wherein the wavelength of light emitted from the active layer is less than 430 nm.

21. The device of claim 1,

wherein the semiconductor layer is made of nitride-based compound semiconductor represented by Al_xGa_1-xN (0≦

x≦

1).

22. A method for fabricating a semiconductor light-emitting device, comprising the steps of:

sequentially forming, on a substrate, at least an n-type semiconductor layer, a semiconductor layer serving as an active layer, and a p-type semiconductor layer;

separating a multilayer structure including the semiconductor layers from the substrate; and

making at least a portion of the n-type semiconductor layer of the multilayer structure porous, the n-type semiconductor layer having a surface serving as a light-extraction surface for extracting light emitted from the active layer.