Nitride semiconductor light-emitting device

Patent metadata

Field	Value
Publication number	US-9437775-B2
Application number	US-201414899364-A
Country	US
Kind code	B2
Filing date	Jun 16, 2014
Priority date	Jun 18, 2013
Publication date	Sep 6, 2016
Grant date	Sep 6, 2016

Abstract

An object is to improve a positive hole injection efficiency into an active layer in a nitride semiconductor light-emitting device. The nitride semiconductor light-emitting device is formed by stacking nitride semiconductor crystals each of which contains Al and has a polar or semipolar surface either serving as a growth face. The device includes an active layer ( 103 ), and first and second composition-graded layers ( 102, 104 ). The active layer ( 103 ) is interposed between the first and second composition-graded layers ( 102, 104 ). Each one of the first and second composition-graded layers is composition-graded so that an Al composition value is rendered smaller as each one of the first and second composition-graded layers ( 102, 104 ) comes close to a side where a sum of spontaneous polarization and piezoelectric polarization is negative.

First claim

The invention claimed is:

1. A nitride semiconductor light-emitting device which is formed by stacking nitride semiconductor crystals in a +c-axis direction, each nitride semiconductor crystal containing Al and having a polar or semipolar surface either serving as a growth face, the device comprising an active layer, a first composition-graded layer and a second composition-graded layer, wherein:
the active layer is interposed between the first and second composition-graded layers; and
each one of the first and second composition-graded layers is composition-graded so that an Al composition value thereof is rendered smaller as each one of the first and second composition-graded layers comes close to a side where a sum of spontaneous polarization and piezoelectric polarization is negative;
the first composition-graded layer has a first interface between the active layer and the first composition-graded layer and a second interface away from the first interface, and the first interface has a larger Al composition value than the second interface; and
the second composition-graded layer has a third interface between the active layer and the second composition-graded layer and a fourth interface away from the third interface and the fourth interface has a smaller Al composition value than the third interface.

2. The device according to claim 1 , further comprising a p-type electron blocking layer disposed to be adjacent to the first or second composition-graded layer, the p-type electron blocking layer being further disposed to be adjacent to the side where the Al composition value is reduced, wherein:
a p-type impurity is doped into the p-type electron blocking layer while the p-type electron blocking layer contains Al;
the p-type electron blocking layer is composition-graded so that an Al composition value thereof is rendered larger as the p-type electron blocking layer comes close to a side which is parted away from the active layer; and
the Al composition value of the p-type electron blocking layer has a maximum value which is larger than the Al composition values of the first and second composition-graded layers.

3. The device according to claim 1 , wherein the first and second composition-graded layers have respective Al composition values at interfaces between each composition-graded layer and the active layer, the Al composition values being substantially equal to each other.

4. The device according to claim 1 , wherein the growth face is a c-plane.

5. The device according to claim 1 , wherein the first and second composition-graded layers are AlGaN layers.

6. The device according to claim 2 , wherein the first and second composition-graded layers have respective Al composition values at interfaces between each composition-graded layer and the active layer, the Al composition values being substantially equal to each other.

7. The device according to claim 6 , wherein the growth face is a c-plane.

8. The device according to claim 7 , wherein the first and second composition-graded layers are AlGaN layers.

Assignees

• Univ Meijo

Inventors

• Takeuchi Tetsuya
• Iwaya Motoaki
• Akasaki Isamu

Classifications

• H01S5/320225

  polar orientation · CPC title

• H01S5/3054

  p-doping · CPC title

• H01S5/3409

  special GRINSCH structures · CPC title

• H01S5/3213

  asymmetric clading layers · CPC title

• H01S5/34333

  with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser · CPC title