Compound semiconductor device and manufacturing method thereof

A compound semiconductor device, comprising:

• a first electrode;
• an intrinsic first compound semiconductor layer over the first electrode;
• a second compound semiconductor layer whose band gap is smaller than that of the first compound semiconductor layer on the first compound semiconductor layer;
• a second electrode over the second compound semiconductor layer, and
• a third compound semiconductor layer whose band gap is smaller than that of the first compound semiconductor layer between the first electrode and the first compound semiconductor layer, wherein
• the first compound semiconductor layer and the second compound semiconductor layer are in direct contact with each other,
• the second compound semiconductor layer and the second electrode are in direct contact with each other, and
• the first compound semiconductor layer and the third compound semiconductor layer are in direct contact with each other.

A compound semiconductor device, comprising:

• a first electrode;
• an intrinsic first compound semiconductor layer over the first electrode;
• a second compound semiconductor layer whose band gap is smaller than that of the first compound semiconductor layer on the first compound semiconductor layer;
• and
• a second electrode over the second compound semiconductor layer, wherein
• the first compound semiconductor layer and the second compound semiconductor layer are in direct contact with each other,
• the second compound semiconductor layer and the second electrode are in direct contact with each other, and
• at least a part of the second compound semiconductor layer is doped to p-type.

A manufacturing method of a compound semiconductor device, comprising:

• forming an intrinsic first compound semiconductor layer over a first electrode;
• forming a second compound semiconductor layer whose band gap is smaller than that of the first compound semiconductor layer on the first compound semiconductor layer;
• and
• forming a second electrode over the second compound semiconductor layer, wherein
• the first compound semiconductor layer and the second compound semiconductor layer are in direct contact with each other,
• the second compound semiconductor layer and the second electrode are in direct contact with each other,
• the second compound semiconductor layer is an electron transit layer,
• the second electrode contains a source electrode, a gate electrode, and a drain electrode, and
• the method comprises further forming an electron supply layer over the second compound semiconductor layer between the forming the second compound semiconductor layer and the forming the second electrode.

A manufacturing method of a compound semiconductor device, comprising:

• forming an intrinsic first compound semiconductor layer over a first electrode;
• forming a second compound semiconductor layer whose band gap is smaller than that of the first compound semiconductor layer on the first compound semiconductor layer;
• and
• forming a second electrode over the second compound semiconductor layer, wherein
• the first compound semiconductor layer and the second compound semiconductor layer are in direct contact with each other,
• the second compound semiconductor layer and the second electrode are in direct contact with each other, and
• the method further comprises forming a third compound semiconductor layer whose band gap is smaller than that of the first compound semiconductor layer over the first electrode, before the forming the first compound semiconductor layer, wherein the first compound semiconductor layer and the third compound semiconductor layer are in direct contact with each other.