Nitride semiconductor laser diode

• US 8,514,904 B2
• Filed: 07/26/2010
• Issued: 08/20/2013
• Est. Priority Date: 07/31/2009
• Status: Active Grant

• Current Assignee: Nichia Corporation
• Original Assignee: Nichia Corporation
• Inventors: Miyoshi, Takashi
• Primary Examiner(s): Park, Kinam
• Application Number:
  US13/387,855
• Publication Number:
  US 20120189030A1
• Time in Patent Office: 1,121 Days
• Field of Search: 372/45.012, 372/45.01, 372/44.01, 372/44.011
• US Class Current: 372/45.012
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01S 5/0021 Degradation or life time measurements
• CPC Class Codes: H01S 5/22 having a ridge or stripe structure
• CPC Class Codes: H01S 5/3013 AIIIBV compounds
• CPC Class Codes: H01S 5/3063 using Mg
• CPC Class Codes: H01S 5/34 comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers H01S5/36 takes precedence
• CPC Class Codes: H01S 5/34333 with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser

Abstract

A nitride semiconductor laser diode includes a substrate, an n-side nitride semiconductor layer formed on the substrate, an active layer formed on the n-side nitride semiconductor layer and having a light emitting layer including In_xAl_yGa_1-x-yN (0<x<1, 0 y<1, 0<x+y<1), and a p-side nitride semiconductor layer formed on the active layer. In the nitride semiconductor laser diode, the lasing wavelength of the nitride semiconductor laser diode is 500 nm or greater, dislocations originated in the active layer penetrate through the p-side nitride semiconductor layer, with the dislocation density in the p-side nitride semiconductor layer being 1×10⁶ cm⁻² or greater, and the concentration distribution of p-type impurities in the depth direction is such that, from the light emitting layer toward the surface of the p-side nitride semiconductor layer, the concentration of the p-type impurity reaches a maximum value of 5×10¹⁸ cm⁻³ or greater within a range of 300 nm from the top portion of the light emitting layer which is closest to the p-side nitride semiconductor layer, and after reaching the maximum value, the concentration remains at 6×10¹⁷ cm⁻³ or greater in the above-described range of 300 nm.

Claims

1. A nitride semiconductor laser diode comprising:

a substrate;

an n-side nitride semiconductor layer containing an n-type impurity and disposed on the substrate;

an active layer having a light emitting layer including In_xAl_yGa_1-x-yN (0<

x<

1, 0≦

y<

1, and 0<

x+y<

1) and disposed on the n-side nitride semiconductor layer; and

a p-side nitride semiconductor layer containing a p-type impurity and disposed on the active layer;

wherein a lasing wavelength of the nitride semiconductor laser diode is 500 nm or greater,

dislocations originated in the active layer penetrate through the p-side nitride semiconductor layer with a dislocation density of 1×

10⁶ cm<sup>−

2</sup> or greater, and

a concentration distribution of the p-type impurity in a depth direction from the light emitting layer toward the surface of the p-side nitride semiconductor layer has a local maximum with the concentration of the p-type impurity of 5×

10¹⁸ cm<sup>−

3</sup> or greater in a range within 300 nm from the top surface of the light emitting layer which is closest to the p-side nitride semiconductor layer, and after passing the local maximum, the concentration of the p-type impurity is not less than 6×

10¹⁷ cm<sup>−

3</sup> in the range within 300 nm.

2. The nitride semiconductor diode according to claim 1, wherein the local maximum is arranged within 150 nm from the top surface of the light emitting element which is closest to the p-side nitride semiconductor layer.

3. The nitride semiconductor laser diode according to claim 1, wherein the concentration distribution of the p-type impurity in a depth direction reaches a local minimum of not less than 6×

10¹⁷ cm<sup>−

3</sup> after passing the local maximum and in the range within 300 nm and, after passing the local minimum, increases to 1×

10¹⁸ cm<sup>−

3</sup> or greater.

4. The nitride semiconductor diode according to claim 3, wherein the local minimum is arranged within 250 nm from the top surface of the light emitting element which is closest to the p-side nitride semiconductor layer.

12. The nitride semiconductor laser diode according to claim 1, wherein the lasing wavelength is 560 nm or less.

13. The nitride semiconductor laser diode according to claim 1, wherein the substrate is made of a nitride semiconductor having a dislocation density of 1×

10⁷ cm<sup>−

2</sup> or less.

14. The nitride semiconductor laser diode according to claim 1, wherein the dislocation density of the substrate is lower than the dislocation density generated in the active layer.

15. A display apparatus comprising a nitride semiconductor laser diode having a lasing wavelength of 500 to 560 nm according to claim 1, a nitride semiconductor laser diode having a lasing wavelength of 440 to 480 nm, and a nitride semiconductor laser diode having a lasing wavelength of 600 to 660 nm.

5. A nitride semiconductor laser diode comprising;

a substrate;

an n-side nitride semiconductor layer containing an n-type impurity and disposed on the substrate;

an active layer of a quantum well structure including a well layer including In_xAl_yGa_1-x-yN (0<

x<

1, 0≦

y<

1, 0<

x+y<

1), and disposed on the n-side nitride semiconductor layer; and

a p-side nitride semiconductor layer containing a p-type impurity and disposed on the active layer;

wherein the n-side nitride semiconductor layer includes a GaN layer or AlGaN layer

the well layer in the active layer has a lasing wavelength of 500 nm or greater,

dislocations originated in the well layer penetrate through the p-side nitride semiconductor layer so that a dislocation density is 1×

10⁶ cm<sup>−

2</sup> or greater in the p-side nitride semiconductor layer, and

wherein the nitride semiconductor laser diode comprises a first p-type nitride semiconductor layer in a range within 300 nm from the top surface of the well layer which is closest to the p-side nitride semiconductor layer, the first p-type nitride semiconductor layer being made of an Al-containing nitride semiconductor, having a bandgap larger than that of the well layer and having a p-type impurity concentration of 5×

10¹⁸ cm<sup>−

3</sup> or greater and

a second p-type semiconductor layer on the first p-type nitride semiconductor layer, the second p-type semiconductor layer having, within the 300 nm range, a p-type impurity concentration smaller than a p-type impurity concentration in the first p-type semiconductor layer and not smaller than 6×

10¹⁷ cm<sup>−

3</sup>.

6. The nitride semiconductor diode according to claim 5, wherein the first p-type nitride semiconductor layer is located within 150 nm from the top surface of the well layer which is closest to the p-side nitride semiconductor layer.

7. The nitride semiconductor laser diode according to claim 5, wherein the concentration of the p-type impurity in the second p-type nitride semiconductor layer decreases with distance from an interface closer to the first p-type nitride semiconductor layer to a degree not less than 6×

10¹⁷ cm<sup>−

3</sup>, and then increases toward an interface of the opposite side.

8. The nitride semiconductor diode according to claim 5, wherein the concentration of the p-type impurity in the second p-type nitride semiconductor layer has a local minimum within 250 nm from the top surface of the well layer which is closest to the p-side nitride semiconductor layer.

9. The nitride semiconductor diode according to claim 5, wherein the concentration of p-type impurity in the second p-type nitride semiconductor layer is 1×

10¹⁸ cm<sup>−

3</sup> or greater at a location 300 nm from the top surface of the well layer which is closest to the p-side nitride semiconductor layer.

10. The nitride semiconductor laser diode according to claim 5, having a third p-type nitride semiconductor layer on the second p-type nitride semiconductor layer, the third p-type nitride semiconductor layer having a band gap larger than the band gap of the second p-type nitride semiconductor layer and smaller than the band gap of the first p-type nitride semiconductor layer.

11. A nitride semiconductor laser diode comprising:

a substrate;

an n-side nitride semiconductor layer containing an n-type impurity and disposed on the substrate;

an active layer of a multi quantum well structure having a well layer including In_xAl_yGa_1-x-yN (0<

x<

1, 0≦

y<

1, 0<

x+y<

1), and disposed on the n-side nitride semiconductor layer; and

a p-side nitride semiconductor layer containing a p-type impurity and disposed on the active layer;

wherein the n-side nitride semiconductor layer includes a GaN layer or AlGaN layer,

the active layer includes a well layer having lasing wavelength of 500 nm or greater and a barrier layer located closest to the p-side in the active layer and having a thickness of 300 nm or less,

the p-side nitride semiconductor layer includes, from the side closer to the active layer,

a first p-type nitride semiconductor layer made of a nitride semiconductor containing Al having a band gap larger than the band gap of the well layer, having a p-type impurity with a concentration of 5×

10¹⁸ cm<sup>−

3</sup> or greater, and having a thickness of 3 to 50 nm,

a second p-type nitride semiconductor layer having a p-type impurity concentration smaller than a p-type impurity concentration of the first semiconductor layer and not smaller than 6×

10¹⁷ cm<sup>−

3</sup>,

a third p-type nitride semiconductor layer having a band gap larger than the band gap of the second p-type nitride semiconductor layer and smaller than the band gap of the first p-type nitride semiconductor layer, and

a fourth p-type nitride semiconductor layer having a p-type impurity concentration of 5×

10¹⁹ cm³ or greater;

wherein dislocations originated in the well layer penetrate through the p-side nitride semiconductor layer and the dislocation density of the p-side nitride semiconductor layer is 1×

10⁶ cm<sup>−

2</sup> or greater.