Metal semiconductor FET having doped A1GaAs layer between channel layer and A1GaAs buffer layer

摘要

A metal-semiconductor field effect transistor includes an AlGaAs buffer layer made of Al.sub.x Ga.sub.1-x As, wherein 0 x 0.4, and a channel layer made of an n-type doped In.sub.y Ga.sub.1-y As, wherein 0 y 0.4, having a thickness equal to or less than a critical thickness for lattice-matching with GaAs. Further, a doped AlGaAs layer is interposed between the AlGaAs buffer layer and the channel layer. The doped AlGaAs layer is made of Al.sub.x Ga.sub.1-x As, wherein 0 x 0.4, is doped with Si of a concentration of 5*10. sup. 17 cm.sup.-3 or more, and has a thickness which is sufficient to provide a barrier against holes caused by a donor depletion region.