Field effect transistor.

摘要

A field effect transistor comprising a substrate made of one conductive type or semiinsulator of semiconductor, working layers formed on the substrate, a source region and drain region provided in the working layer and channel region between the source and drain region and gate electrode formed on the channel region, said working layers comprising a first semiconductor layer of Ga In As mixed crystal formed on the substrate and a second semiconductor layer formed on the first semiconductor layer and made of AI In As mixed crystal containing n type impurity in such a manner that the density of the impurity is less in the region near the gate electrode and more in the region near the second semiconductor layer.