Light-emitting element having nitride semiconductor multiquantum barrier, and process for production thereof

• US 9,059,354 B2
• Filed: 05/02/2014
• Issued: 06/16/2015
• Est. Priority Date: 02/24/2010
• Status: Active Grant

• Current Assignee: Riken
• Original Assignee: Riken
• Inventors: Hirayama, Hideki
• Primary Examiner(s): Potter, Roy
• Assistant Examiner(s): PATTON, PAUL E
• Application Number:
  US14/268,267
• Publication Number:
  US 20140239252A1
• Time in Patent Office: 410 Days
• Field of Search: 257/13, 257/14, 257/15, 257/E33.008, 257/E33.027, 257/E33.028, 438/47
• US Class Current: 1/1
• CPC Class Codes: H01L 33/04 with a quantum effect structure or superlattice, e.g. tunnel junction
• CPC Class Codes: H01L 33/06 within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: H01L 33/32 containing nitrogen

Abstract

An Al_0.95Ga_0.05N:Mg (25 nm) single electron barrier can stop electrons having energy levels lower than the barrier height. Meanwhile, a 5-layer Al_0.95Ga_0.05N (4 nm)/Al_0.77Ga_0.23N (2 nm) MQB has quantum-mechanical effects so as to stop electrons having energy levels higher than the barrier height. Thus, electrons having energy levels higher than the barrier height can be blocked by making use of multiquantum MQB effects upon electrons. The present inventors found that the use of an MQB allows blocking of electrons having higher energy levels than those blocked using an SQB. In particular, for InAlGaN-based ultraviolet elements, AlGaN having the composition similar to that of AlN is used; however, it is difficult to realize a barrier having the barrier height exceeding that of AlN. Therefore, MQB effects are very important. Accordingly, it becomes possible to provide element technology for further improving deep UV light emission intensity using, as a light-emitting layer material, an AlGaInN-based material and, in particular, an AlGaN-based material.

Claims

1. A nitride semiconductor light-emitting element that emits light at a wavelength of 220 to 390 nm, comprising:

an Al_yGa_1-yN (0≦

y≦

1) buffer layer disposed on a substrate;

an Al_y0Ga_1-y0N (0≦

y0≦

1) n-type layer disposed on the buffer layer;

a quantum-well light-emitting layer comprising an Al_y1Ga_1-y1N quantum well layer and an Al_y2Ga_1-y2N barrier layer (0≦

y1<

y2≦

1) disposed on the n-type layer;

an Al_y3Ga_1-y3N (0≦

y3≦

1) p-type layer disposed on the quantum-well light-emitting layer; and

a multiquantum-barrier electron-blocking layer disposed on the p-type layer,

wherein the multiquantum-barrier electron-blocking layer comprises alternately layered pairs of an Al_y4Ga_1-y4N barrier layer and an Al_y5Ga_1-y5N valley layer (0≦

y5<

y4≦

1) with a constant thickness period or with a 1st thickness period and a 2nd thickness period that differs from the 1st thickness period, and,

wherein a thickness period for the alternate layers increases or decreases in a stepwise manner from the quantum-well light emitting layer side to an opposite side to the substrate.

8. An electric apparatus comprising a light source with the nitride semiconductor light-emitting element according to any of claim 1.

2. A nitride semiconductor light-emitting element that emits light at a wavelength of 220 to 390 nm, comprising:

an Al_yGa_1-yN (0≦

y≦

1) buffer layer disposed on a substrate;

an Al_y0Ga_1-y0N (0≦

y0≦

1) n-type layer disposed on the buffer layer;

a quantum-well light-emitting layer comprising an Al_y1Ga_1-y1N quantum well layer and an Al_y2Ga_1-y2N barrier layer (0≦

y1<

y2≦

1) disposed on the n-type layer;

an Al_y3Ga_1-y3N (0≦

y3≦

1) p-type layer disposed on the quantum-well light-emitting layer; and

a multiquantum-barrier electron-blocking layer disposed on the p-type layer,

wherein the multiquantum-barrier electron-blocking layer is a non-polar layer disposed on an A-plane or M-plane or a layer disposed on a semipolar plane of an underlying crystal for the multiquantum-barrier electron-blocking layer.

9. An electric apparatus comprising a light source with the nitride semiconductor light-emitting element according to any of claim 2.

3. A process for growing a light-emitting element structure on a group-III nitride single crystal, comprising the steps of:

growing an AlyGa1-yN (0≦

y≦

1) buffer layer on a substrate;

growing an Al_y0Ga_1-y0N (0≦

y0≦

1) n-type layer on the buffer layer;

growing a quantum-well light-emitting layer comprising an Al_y1Ga_1-y1N quantum well layer and an Al_y2Ga_1-y2N barrier layer (0≦

y1<

y2≦

1) on the n-type layer;

growing an Al_y3Ga_1-y3N (0≦

y3≦

1) p-type layer on the quantum-well light-emitting layer; and

growing a multiquantum-barrier electron-blocking layer by alternately layering pairs of an Al_y4Ga_1-y4N barrier layer and an Al_y5Ga_1-y5N valley layer (0≦

y5<

y4≦

1) on the p-type layer

wherein the multiquantum-barrier electron-blocking layer is a non-polar layer disposed on an A-plane or M-plane or a layer disposed on a semipolar plane of an underlying crystal for the multiquantum barrier electron-blocking layer.

4. A nitride semiconductor light-emitting element that emits light at a wavelength of 220 to 390 nm, comprising:

an Al_yGa_1-yN (0≦

y≦

1) buffer layer disposed on a substrate;

an Al_y0Ga_1-y0N (0≦

y0≦

1) n-type layer disposed on the buffer layer;

a quantum-well light-emitting layer comprising an Al_y1Ga_1-y1N quantum well layer and an Al_y2Ga_1-y2N barrier layer (0≦

y1<

y2≦

1) disposed on the n-type layer;

an Al_y3Ga_1-y3N (0≦

y3≦

1) p-type layer disposed on the quantum-well light-emitting layer; and

a multiquantum-barrier electron-blocking layer disposed on the p-type layer, wherein

the multiquantum-barrier electron-blocking layer disposed on the p-type layer comprises a plurality of alternately layered pairs of an Al_y4Ga_1-y4N barrier layer and an Al_y5Ga_1-y5N valley layer (0≦

y5<

y4≦

1),

wherein the alternately layered pairs comprise;

1st pairs of layers and the 2nd pairs of layers that are arranged in that order from the quantum-well light-emitting layer side to an opposite side to the substrate; and

another layer of another pair of layers that is disposed between the 1st pairs of layers and the 2nd pairs of layers, and

wherein a layer thickness of the 1st pairs of layers is greater or less than a layer thickness of the 2nd pairs of layers.

6. The nitride semiconductor light-emitting element according to claim 4, wherein a thickness of the barrier layer and a thickness of valley layer in an identical pairs of layers are the same when measured in units of monolayer.

7. The nitride semiconductor light-emitting element according to claim 4, which is a light-emitting diode.

10. An electric apparatus comprising a light source with the nitride semiconductor light-emitting element according to any of claim 4.

5. A nitride semiconductor light-emitting element that emits light at a wavelength of 220 to 390 nm, comprising:

an Al_yGa_1-yN (0≦

y≦

1) buffer layer disposed on a substrate;

an Al_y0Ga_1-y0N (0≦

y0≦

1) n-type layer disposed on the buffer layer;

a quantum-well light-emitting layer comprising an Al_y1Ga_1-y1N quantum well layer and an Al_y2Ga_1-y2N barrier layer (0≦

y1≦

y2<

1) disposed on the n-type layer;

an Al_y3Ga_1-y3N (0≦

y3≦

1) p-type layer disposed on the quantum-well light-emitting layer; and

a multiquantum-barrier electron-blocking layer disposed on the p-type layer,

wherein

the multiquantum-barrier electron-blocking layer disposed on the p-type layer comprises a plurality of alternately layered pairs of an Al_y4Ga_1-y4N barrier layer and an Al_y5Ga_1-5N valley layer (0≦

y5<

y4≦

1),

wherein the alternately layered pairs include;

1st, 2nd, and 3rd pairs of layers that are arranged in that order from the quantum-well light-emitting layer side to an opposite side to the substrate; and

another layer or another pair of layers that is disposed among the 1st, the 2nd, and the 3rd pairs of layers, and

wherein a layer thickness of the 1st pairs of layers is greater than a layer thickness of the 2nd pairs of layers, and the layer thickness of the 2nd pairs of layers is greater than a layer thickness of the 3rd pairs of layers, or wherein a layer thickness of the 1st pairs of layers is less than a layer thickness of the 2nd pairs of layers, and the layer thickness of the 2nd pairs of layers is less than a layer thickness of the 3rd pairs of layers.

11. An electric apparatus comprising a light source with the nitride semiconductor light-emitting element according to any of claim 5.