High Electron Mobility Transistor Structure

A high electron mobility transistor (HEMT), comprising:

• a first breakdown voltage layer comprising a first resistivity value, wherein the first breakdown voltage layer exhibits a first lattice-constant and is doped with a first dopant at a first doping concentration;
• a second breakdown voltage layer disposed beneath the first breakdown voltage layer and comprising a second resistivity value that is greater than, the first resistivity value, wherein the second breakdown voltage layer exhibits a second lattice-constant that is substantially equal to the first lattice-constant and is doped with a second dopant at a second doping concentration that is greater than the first doping concentration;
• and
• a crystal adaptation layer disposed beneath the second breakdown voltage layer, wherein the crystal adaptation layer exhibits a third lattice-constant which is substantially equal to each of the first and second lattice-constants;
• and wherein the crystal adaptation layer is doped with a third dopant at a third doping concentration that is approximately equal to the first doping concentration.

A transistor, comprising:

• a first breakdown voltage layer of gallium nitride (GaN) comprising a first resistivity value and a first carbon dopant concentration of less than approximately than 1e17 cm−3;
• and
• a second breakdown voltage layer of GaN disposed beneath the first breakdown voltage layer and comprising a second resistivity value and a second carbon dopant concentration larger than approximately than 5e18 cm−3, wherein the first resistivity value is less than the second resistivity value;
• and
• a crystal adaptation layer disposed beneath the second breakdown voltage layer and configured to lattice-match to the second breakdown voltage layer, wherein the crystal adaptation layer comprises a first lattice-constant which is essentially equal to a second lattice-constant of the first breakdown voltage layer and a third lattice-constant of the second breakdown voltage layer, and wherein a third carbon dopant concentration within the crystal adaptation layer is less than approximately than 1e17 cm−3.

A transistor, comprising:

• a first breakdown voltage layer comprising a first carbon dopant concentration, which forms a channel region of the transistor;
• a second breakdown voltage layer formed beneath the first breakdown voltage layer, and comprising a second carbon dopant concentration that is about an order of magnitude greater than the first carbon dopant concentration;
• and
• a crystal adaptation layer formed beneath the second breakdown voltage layer, configured to lattice-match to the second breakdown voltage layer, and comprising a third carbon dopant concentration that is about an order of magnitude less than the second carbon dopant concentration.