| 摘要 |
A nitride based heterojunction transistor includes a substrate and a first Group III nitride layer, such as an AlGaN based layer, on the substrate. The first Group III-nitride based layer has an associated first strain. A second Group III-nitride based layer, such as a GaN based layer, is on the first Group III-nitride based layer. The second Group III-nitride based layer has a bandgap that is less than a bandgap of the first Group III-nitride based lay er and has an associated second strain. The second strain has a magnitude that is greater than a magnitude of the first strain. A third Group III-nitride base d layer, such as an AlGaN or AlN layer, is on the GaN layer. The third Group I II- nitride based layer has a bandgap that is greater than the bandgap of the second Group III-nitride based layer and has an associated third strain. The third strain is of opposite strain type to the second strain. A source contact, a drain contact and a gate contact may be provided on the third Gro up III-nitride based layer. Nitride based heterojunction transistors having an AlGaN based bottom confinement layer, a GaN based channel layer on the botto m confinement layer and an AlGaN based barrier layer on the channel layer, the barrier layer having a higher concentration of aluminum than the bottom confinement layer, are also provided. Methods of fabricating such transistor are also provided.
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