Patent ID: 7030428

Claim:
A nitride based heterojunction transistor structure, comprising: a substrate; a first AlGaN based layer on the substrate, the first AlGaN based layer having a first strain associated therewith; a GaN based layer on the first AlGaN based layer, the GaN based layer having a bandgap that is less than a bandgap of the first AlGaN based layer and having a second strain associated therewith, the second strain having a magnitude that is greater than a magnitude of the first strain; and a second AlGaN based layer on the GaN layer opposite the first AlGaN based layer, the second AlGaN based layer having a bandgap that is greater than the bandgap of the GaN based layer and having a third strain associated therewith, the third strain being of opposite strain type to the second strain, wherein the second AlGaN based layer has a thickness and aluminum concentration large enough to induce formation of a 2D electron gas at the interface with the GaN based layer, but less than a thickness at which cracking or defect formation occurs.