Gallium nitride on silicon with a thermal expansion transition buffer layer

Abstract

A method is provided for forming a matching thermal expansion interface between silicon (Si) and gallium nitride (GaN) films. The method provides a (111) Si substrate with a first thermal expansion coefficient (TEC), and forms a silicon-germanium (SiGe) film overlying the Si substrate. A buffer layer is deposited overlying the SiGe film. The buffer layer may be aluminum nitride (AlN) or aluminum-gallium nitride (AlGaN). A GaN film is deposited overlying the buffer layer having a second TEC, greater than the first TEC. The SiGe film has a third TEC, with a value in between the first and second TECs. In one aspect, a graded SiGe film may be formed having a Ge content ratio in a range of about 0% to 50%, where the Ge content increases with the graded SiGe film thickness.

Dependencies are inferred from the claim text.