Semiconductor device

A semiconductor device comprising:

• a GaAs substrate;
• a buffer layer provided on the GaAs substrate, the buffer layer being made of a semiconductor, and at least a part of the semiconductor having a lattice constant larger than a lattice constant of GaAs;
• a laminated structure provided on the buffer layer, including a channel layer and a electron supply layer, the channel layer being made of Inu1Ga1−u1As, and the electron supply layer being made of n-type Inv1Al1−v1As;
• a Schottky contact layer provided on the laminated structure, at least a part of the Schottky contact layer being made of non-doped Inv2Al1−v2As;
• a n-type Inx(Ga1−yAly)1-xP layer provided on the Schottky contact layer;
• a n-type Inu2Ga1−u2As ohmic contact layer provided on the n-type Inx(Ga1−yAly)1-xP layer;
• a gate electrode provided on the Schottky contact layer;
• and
• a source electrode and a drain electrode provided on the ohmic contact layer,
• the Inx(Ga1−yAly)1-xP layer having a part where a bandgap has a distribution which shows a gradual or a stepwise decrease from the Schottky contact layer toward the ohmic contact layer.

A semiconductor device comprising:

• a GaAs substrate;
• a buffer layer provided on the GaAs substrate, the buffer layer being made of a semiconductor, and at least a part of the semiconductor having a lattice constant larger than a lattice constant of GaAs;
• a laminated structure provided on the buffer layer, including a channel layer and a electron supply layer, the channel layer being made of Inu1Ga1−u1As, and the electron supply layer being made of n-type Inv1Ga1−v1As;
• a Schottky contact layer provided on the laminated structure, at least a part of the Schottky contact layer being made of non-doped Inv2Al1−v2As;
• a n-type Inx(Ga1−yAly) l-XP layer provided on the Schottky contact layer;
• a n-type Inu2Ga1−u2As ohmic contact layer provided on the n-type Inx(Ga1−yAly) l-XP layer;
• a gate electrode provided on the Schottky contact layer;
• and
• a source electrode and a drain electrode provided on the ohmic contact layer,
• the buffer layer having a part where the lattice constant has a distribution which shows a gradual or a stepwise increase from the substrate toward the laminated structure, and
• the Inx(Ga1−yAly) l-XP layer having a part where a bandgap has a distribution which shows a gradual or a stepwise decrease from the Schottky contact layer toward the ohmic contact layer.