Nitride semiconductor device and method for fabricating the same

Abstract

A nitride semiconductor device includes: a first nitride semiconductor whose surface is etched; and a second nitride semiconductor formed on the etched surface of the first nitride semiconductor. Of oxygen, carbon, and silicon contained in the interface between the first and second nitride semiconductors, at least silicon has a concentration equal to or less than one tenth the dopant concentration in the first nitride semiconductor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view schematically showing a semiconductor laser element which is a nitride semiconductor device according to one embodiment of the present invention.

FIG. 2 is a graph showing the relation between the peak concentration of oxygen, carbon, and silicon in the interface between a p-type optical guide layer and a p-type cladding layer and the operating voltage in the semiconductor laser element according to one embodiment of the present invention.

FIG. 3 is a graph showing the relation between the peak concentration of oxygen, carbon, and silicon in the interface between the p-type optical guide layer and the p-type cladding layer and the Mg concentration in the p-type optical guide layer in the semiconductor laser element according to one embodiment of the present invention.

FIGS. 4A to 4E are sectional views showing a method for fabricating a semiconductor laser element according to one embodiment of the present invention in the order of its fabrication process steps.

FIG. 5 is a graph showing the impurity concentrations of magnesium, oxygen, carbon, and silicon in the interface between the p-type optical guide layer and the p-type cladding layer in the semiconductor laser element according to one embodiment of the present invention.

FIG. 6 is a graph showing the impurity concentrations of magnesium, oxygen, carbon, and silicon in the interface between a p-type optical guide layer and a p-type cladding layer in a conventional semiconductor laser element.

Claims

1. A nitride semiconductor device comprising: a first nitride semiconductor whose surface is etched; anda second nitride semiconductor formed on the etched surface of the first nitride semiconductor,wherein of oxygen, carbon, and silicon contained in the interface between the first and second nitride semiconductors, at least silicon has a concentration equal to or less than one tenth the dopant concentration in the first nitride semiconductor.

2. The device of claim 1, wherein the first nitride semiconductor is a p-type nitride semiconductor.

3. The device of claim 1, wherein the second nitride semiconductor is a p-type nitride semiconductor.

4. The device of claim 1, further comprising: a first optical guide layer of a first conductivity type; an active layer; a second optical guide layer of a second conductivity type; and a cladding layer of the second conductivity type, which are each made of a nitride semiconductor and sequentially formed on a substrate, wherein the first nitride semiconductor is the second optical guide layer, and the second nitride semiconductor is the cladding layer.

5. The device of claim 4, further comprising a current blocking layer formed between the second optical guide layer and the cladding layer, having an opening exposing the second optical guide layer, and made of a nitride semiconductor of the first conductivity type.

6. A method for fabricating a nitride semiconductor device, comprising: the step (a) of etching a first nitride semiconductor;the step (b) of removing impurities in the etched surface of the first nitride semiconductor; andthe step (c) of forming a second nitride semiconductor on the etched surface of the first nitride semiconductor.

7. The method of claim 6, further comprising, after the step (b) and before the step (c), the step (d) of subjecting the etched surface of the first nitride semiconductor to heat treatment.

8. The method of claim 7, wherein in the step (d), the heat treatment is performed in an atmosphere containing nitrogen radicals.

9. The method of claim 6, wherein in the step (b), the impurities are removed at a higher temperature than a temperature at which the second nitride semiconductor is formed in the step (c).

10. The method of claim 6, wherein in the step (b), the impurities are removed by etching with a gas containing at least hydrogen.

11. The method of claim 6, wherein in the step (b), the impurities are removed by etching with a gas containing at least hydrogen chloride.

12. The method of claim 6, wherein of oxygen, carbon, and silicon, at least silicon constitutes the impurities.

13. The method of claim 6, wherein the first and second nitride semiconductors are p-type nitride semiconductors.

14. The method of claim 6, further comprising: the step (e) of sequentially forming, on a substrate, a first cladding layer of a first conductivity type, a first optical guide layer of the first conductivity type, an active layer, a second optical guide layer of a second conductivity type as the first nitride semiconductor, and a current blocking layer of the first conductivity type, which are each made of a nitride semiconductor;the step (f) of forming, by etching, an opening through the current blocking layer, the opening exposing the second optical guide layer; andthe step (g) of forming a second cladding layer of the second conductivity type on the current blocking layer with the opening formed therethrough and on a portion of the second optical guide layer exposed from the opening, the second cladding layer serving as the second nitride semiconductor,wherein the step (b) is the step of removing impurities in the etched surface of the second optical guide layer, andthe step (c) is the step of forming the second cladding layer on the etched surface of the second optical guide layer.