Compound semiconductor device and method for manufacturing the same

1. A compound semiconductor device comprising:

a substrate;

a nitride semiconductor layer formed over the substrate;

a first barrier layer of a nitride semiconductor formed over the substrate a part of a first region of the nitride semiconductor layer;

a first collector electrode formed over another part of the first region of the nitride semiconductor layer;

a first well layer of a nitride semiconductor formed over the first barrier layer;

a second barrier layer of a nitride semiconductor formed over the first well layer;

a first emitter electrode formed over the second barrier layer;

a third barrier layer of a nitride semiconductor formed over a part of a second region of the nitride semiconductor layer, the second region is adjacent to the first region;

a second collector electrode formed over another part of the second region of the nitride semiconductor layer;

a second well layer of a nitride semiconductor formed over the third barrier layer;

a fourth barrier layer of a nitride semiconductor formed over the second well layer; and

a second emitter electrode formed over the fourth barrier layer, wherein

an upper surface of the first region of the nitride semiconductor layer, an upper surface of the first barrier layer, an upper surface of the first well layer, and an upper surface of the second barrier layer have a (0001) plane in terms of crystal orientation,

an upper surface of the second region of the nitride semiconductor layer, an upper surface of the third barrier layer, an upper surface of the second well layer, and an upper surface of the fourth barrier layer have a (000-1) plane in terms of crystal orientation,

the first emitter electrode and the second emitter electrode are electrically coupled to each other, and

the first collector electrode and the second collector electrode are electrically coupled to each other.

2. The compound semiconductor device according to claim 1 ,

wherein the first barrier layer, the second barrier layer, the third barrier layer and the second barrier layer each include an In x Al y Ga 1-x-y N (0≤x<1, 0≤y<1, 0<x+y<1) layer, and

the first well layer and second well layer each includes an In z Ga 1-z N (0≤z<1) layer.

3. The compound semiconductor device according to claim 1 ,

wherein an ion-implanted region is formed at a boundary between the first and the third barrier layers, between the first and the second well layers, and between the second and the fourth barrier layers.

4. The compound semiconductor device according to claim 1 ,

wherein a passivation film is formed at a boundary between the first and the third barrier layers, between the first and the second well layers, and between the second and the fourth barrier layers.

5. The compound semiconductor device according to claim 1 ,

wherein the substrate is a sapphire substrate, a silicon carbide substrate, a gallium nitride substrate, or an aluminum nitride substrate.

6. The compound semiconductor device according to claim 1 ,

wherein the first emitter electrode and the second emitter electrode are integrated with each other, and

the first collector electrode and the second collector electrode are integrated with each other.

7. The compound semiconductor device according to claim 1 , further comprising:

a high-electron mobility transistor formed on the substrate.