GaN-series light emitting diode with high light efficiency and the manufacturing method

• US 20070108457A1
• Filed: 12/29/2006
• Published: 05/17/2007
• Est. Priority Date: 09/27/2004
• Status: Active Grant

• Current Assignee: Semileds Optoelectronics Company Limited (SemiLEDs Inc)
• Original Assignee: Supernova Optoelectronics Corp.
• Inventors: Hon, Schang-Jin, Lai, Mu-Jen
• Granted Patent: US 7,772,607 B2
• Time in Patent Office: Days
• US Class Current: 257/94
• CPC Class Codes: H01L 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/14 with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/32 containing nitrogen

Abstract

A GaN-series light emitting diode with high light efficiency utilizes a p-type semiconductor layer having a textured surface structure. The optical waveguide effect can be interrupted and formation of hexagonal shaped pits defect can be reduced due to the textured structure. The p-type semiconductor layer is formed on a light emitting layer and includes a p-type cladding layer, p-type transitional layer, and p-type ohmic contact layer. During the manufacturing of the GaN-series LED, the tension and compression of strain is controlled while the p-type cladding layer and the p-type transition layer are formed. Through the control of the epitaxial growth process, it is attained that the surface of the p-type semiconductor layer is textured to increase external quantum efficiency and the operation life of the light emitting device.

Claims

1. A GaN-series light emitting diode having a high light efficiency, comprising:

a substrate;

a semiconductor layer formed on said substrate and including an n-type semiconductor layer, a light emitting layer, and a p-type semiconductor layer,

wherein said light emitting layer is sandwiched between said n-type semiconductor layer and said p-type semiconductor layer, and wherein said p-type semiconductor layer includes a p-type cladding layer, a p-type transition layer and a p-type ohmic contact layer sequentially formed on said light emitting layer, and wherein said p-type semiconductor layer has a textured surface formed during epitaxial growth of said p-type semiconductor layer as the result of a strain created in said p-type cladding layer, said textured surface being substantially void of hexagonally shaped defects and further comprising a Distributed Bragg Reflector connected with said light emitting layer and located directly below said light emitting layer.

2. The GaN-series light emitting diode in accordance with claim 1, wherein said textured surface of said p-type semiconductor layer interrupts optical waveguide effect in said light emitting diode.

3. The GaN-series light emitting diode in accordance with claim 1, wherein said textured surface of said p-type semiconductor layer is formed by controlling the strain of said p-type cladding layer and said p-type transition layer during the epitaxial growth of said p-type semiconductor layer.

4. The GaN-series light emitting diode in accordance with claim 1, wherein said substrate is selected from a group consisting of sapphire, silicon carbide, zinc oxide, zirconium diboride, gallium arsenide and silicon.

5. The GaN-series light emitting diode in accordance with claim 1, wherein said n-type semiconductor layer is formed from N-B_xAl_yIn_z, Ga_1-x-y-zN_pAS_q (0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, 0≦

p<

1, 0≦

q≦

1, and x+y+z<

1, p+q=1), or N-B_xAl_yIn_zGa_1-x-y-zN_pP_q(0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, 0≦

p≦

1, 0≦

q≦

1, and x+y+z<

1, p+q=1).

6. The GaN-series light emitting diode in accordance with claim 1, wherein said p-type semiconductor layer includes P-B_xAl_yIn_zGa_1-x-y-zN_pAs_q (0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, 0≦

p≦

1, 0≦

q≦

1, and x+y+z<

1, p+q=1), or P-B_xAl_yIn_zGa_1-x-y-zN_pP_q(0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, 0≦

p≦

1, 0≦

q≦

1, and x+y+z<

1, p+q=1).

7. The GaN-series light emitting diode in accordance with claim 1, wherein said light emitting layer includes B_xAl_yIn_zGa_1-x-y-zN_pAs_q(0≦

x≦

1, 0≦

y≦

1, 0≦

z≦

1, 0≦

p≦

1, 0≦

q≦

1, and x+y+z<

1, p+q=1), or B_xAl_yIn_zGa_1-x-y-zN_pP_q(0≦

X≦

1, 0≦

y≦

1, 0≦

z≦

1, 0≦

p≦

1, 0≦

q≦

1, and x+y+z<

1, p+q=1), or combination thereof to form quantum well structure.

8. The GaN-series light emitting diode in accordance with claim 1, wherein said p-type cladding layer is a cladding layer having the tension strain controlled during epitaxial growth thereof.

9. The GaN-series light emitting diode in accordance with claim 1, wherein said p-type transition layer is a superlattice structure composed by a semiconductor layer.

10. The GaN-series light emitting diode in accordance with claim 1, wherein said p-type ohmic contact layer is a superlattice structure composed by a semiconductor layer.

11. The GaN-series light emitting diode in accordance with claim 1, wherein a concentration of dopants in said p-type cladding layer includes a concentration of magnesium in a range from 5×

10¹⁹ to 5×

10²⁰ cm<sup>−

3</sup>.

12. The GaN-series light emitting diode in accordance with claim 1, wherein a concentration of dopants in said p-type transition layer includes a concentration of magnesium in a range from 5×

10¹⁷ to 5×

10⁹cm<sup>−

3</sup>.

13. The GaN-series light emitting diode in accordance with claim 11 or 12, wherein said superlattice structure includes a plurality of stacked semiconductor layers having different compositions, thickness, and dopants concentrations.

14. The GaN-series light emitting diode in accordance with claim 1, wherein said reflection layer is formed as a Distributed Bragg Reflector including a plurality of stacked semiconductor layers.

15. A GaN-series light emitting diode having a high light efficiency, comprising:

a substrate;

a n-type nitride semiconductor contact layer formed on said substrate;

a nitride semiconductor light emitting layer formed on said n-type nitride semiconductor contact layer;

a p-type nitride semiconductor layer having a nitrogen-polarity surface and the p-type nitride semiconductor layer formed on said nitride semiconductor light emitting layer;

wherein said the p-type nitride semiconductor layer is composed of a p-type cladding layer including a doping concentration of magnesium is in a range of from 5×

10¹⁹ to 5×

10²⁰ cm<sup>−

3</sup>, a p-type transition layer including a doping concentration of magnesium is in a range of from 5×

10¹⁷ to 5×

10¹⁹ cm<sup>−

3</sup> and a p-type ohmic contact layer including a doping concentration of magnesium is between said p-type cladding layer and said p-type transition layer.

16. The GaN-series light emitting diode in accordance with claim 15, wherein said nitrogen-polarity surface is generated from controlling the magnesium doping profile during epitaxy of p-type nitride semiconductor layer.

17. The GaN-series light emitting diode in accordance with claim 15, wherein said nitrogen-polarity surface is a textured surface and the textured surface is free from defect pits.

18. The GaN-series light emitting diode in accordance with claim 15, wherein said p-type cladding layer is as a stimulation that increases the tension strain.

19. The GaN-series light emitting diode in accordance with claim 15, wherein said p-type transition layer is as a strain modulation layer that decreases the tension strain.

20. A GaN-series light emitting diode having a high light efficiency, comprising:

a substrate;

a n-type nitride semiconductor contact layer formed on the said substrate;

a nitride semiconductor light emitting layer formed on said n-type nitride semiconductor contact layer;

a p-type nitride semiconductor cladding layer is formed on said nitride semiconductor light emitting layer;

a p-type nitride semiconductor transition layer formed on said p-type nitride semiconductor cladding layer;

a p-type nitride semiconductor ohmic contact layer formed on said p-type nitride semiconductor transition layer;

and at least one metal monolayer structures formed between said p-type nitride semiconductor cladding layer and said p-type nitride semiconductor transition layers.

21. The GaN-series light emitting diode in accordance with claim 20, wherein said metal monolayer structure is selected from consisting of aliminum, gallium, indium and other III-group elements.

22. The GaN-series light emitting diode in accordance with claim 20, wherein said p-type nitride semiconductor ohmic contact layer has a textured surface.

23. The GaN-series light emitting diode in accordance with claim 22, wherein said textured surface of said p-type semiconductor ohmic contact layer is a nitrogen-polarity surface and the nitrogen-polarity surface is free from defect pits.