| 摘要 |
A field effect transistor includes a buffer layer, an undoped channel layer, and a N-type electron supplying layer which are sequentially deposited on a semi-insulating semiconductor substrate. The undoped channel layer is formed of an InxGa1-xAs layer. The In composition ratio in the InGaAs layer varies gradually in the direction of the thickness and has a maximum value at the position spaced away from the interface of the N-type electron supplying layer of the InGaAs layer by 40 ANGSTROM or more but less than 110 ANGSTROM .
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