| 摘要 |
PROBLEM TO BE SOLVED: To provide the design rule of an epitaxial film structure essential for satisfying both large current drive capacity and good pinch-off characteristics. SOLUTION: In a field effect transistor formed by laminating a buffer layer and a channel layer of compound semiconductor on a GaAs substrate or an Si substrate, the buffer layer and a channel layer are formed of a layer, including III-V compound semiconductor layer comprising one group III element A and a group V element B. An n-type quantum well layer comprising CxA1-x, having band gap smaller than that of III-V compound semiconductor and containing other element C, is formed on the buffer layer side of a channel layer. Composition ratio x of the n-type quantum well layer is varied continuously as a function of a film thickness d from the buffer layer, so that the relation x=cdn is satisfied, moreover with n>=1. The n-type quantum well layer is formed thinner than a critical thickness which causes misfit dislocation of between lattices. |
