Semiconductor Device and Method of Manufacturing the Same

1 . A method for manufacturing a semiconductor device, the method comprising:

a first step of forming a p-GaN layer including p-type GaN on a substrate, the p-GaN layer having an N polar surface;

a second step of forming an AlGaN layer including undoped AlGaN on the p-GaN layer, the AlGaN layer having an N polar surface;

a third step of oxidizing a surface of the AlGaN layer to form a surface oxidized layer including AlGaON;

a fourth step of forming an electrode including an electrode material containing Ni on the surface oxidized layer, the electrode being in contact with the surface oxidized layer; and

a fifth step of forming an oxide layer including an oxide of the electrode material by heating in a portion of the electrode in contact with the surface oxidized layer, the oxide layer formed between the electrode and the AlGaN layer and in contact with both the AlGaN layer and the electrode.

2 . The method for manufacturing a semiconductor device according to claim 1 , wherein

the oxide layer is in ohmic contact with a two-dimensional hole gas formed in the vicinity of an interface of the p-GaN layer with the AlGaN layer.

3 . A semiconductor device comprising:

a p-GaN layer including p-type GaN and formed on a substrate, the p-GaN layer having an N polar surface;

an AlGaN layer including undoped AlGaN and formed on the p-GaN layer, the AlGaN layer having an N polar surface;

an electrode including an electrode material containing Ni and formed on the AlGaN layer; and

an oxide layer including an oxide of the electrode material, the oxide layer formed between the AlGaN layer and the electrode and being in contact with both the AlGaN layer and the electrode.

4 . The semiconductor device according to claim 3 , wherein

the oxide layer is in ohmic contact with a two-dimensional hole gas formed in the vicinity of an interface of the p-GaN layer with the AlGaN layer.

5 . A method for manufacturing a semiconductor device, the method comprising:

a first step of forming a collector layer including GaN on a substrate, the collector layer having an N polar surface;

a second step of forming a base layer including p-type GaN on the collector layer, the base layer having an N polar surface;

a third step of forming an emitter layer including undoped AlGaN on the base layer, the emitter layer having an N polar surface;

a fourth step of forming an emitter electrode on the emitter layer;

a fifth step of oxidizing a surface of the emitter layer positioned around the emitter electrode to form a surface oxidized layer including AlGaON;

a sixth step of forming a base electrode including an electrode material containing Ni on the surface oxidized layer, the base electrode being in contact with the surface oxidized layer;

a seventh step of forming an oxide layer including an oxide of the electrode material by heating in a portion of the base electrode in contact with the surface oxidized layer, the oxide layer formed between between the base electrode and the emitter layer and being in contact with both the emitter layer and the base electrode; and

an eighth step of forming a collector electrode electrically connected to the collector layer.

6 . The method for manufacturing a semiconductor device according to claim 5 , wherein

the oxide layer is in ohmic contact with a two-dimensional hole gas formed in the vicinity of an interface of the base layer with the emitter layer.

7 . A semiconductor device comprising:

a collector layer including GaN and formed on a substrate, the collector layer having an N polar surface;

a base layer including p-type GaN formed on the collector layer, the base layer having an N polar surface;

an emitter layer including undoped AlGaN formed on the base layer, the emitter layer having an N polar surface;

an emitter electrode formed on the emitter layer;

a base electrode including an electrode material containing Ni and formed on the emitter layer around the emitter electrode;

an oxide layer including an oxide of the electrode material, the oxide layer formed between the emitter layer and the base electrode and being in contact with both the emitter layer and the base electrode; and

a collector electrode electrically connected to the collector layer.

8 . The semiconductor device according to claim 7 ,

wherein the oxide layer is in ohmic contact with a two-dimensional hole gas formed in the vicinity of an interface of the base layer with the emitter layer.