GaAs FET with a degenerate semiconductor gate

A new GaAs FET structure has been proposed and examined experimentally in which the gate material is degenerate p-Al0.3Ga0.7As fabricated directly on to a p-type layer of undoped semi-insulating GaAs substrates. Obtained transconductance was 207mS/mm under the gate bias of 2V for the gate length of2microm and the onset voltage of the gate leakage current was 0.5-0. 6V higher than that of MESFETs. These characteristics were explained by the presence of an n-type inversion layer located at p-AlGaAs/p-GaAs interface. Temperature dependence of the drain current leads to a conclusion that the Fermi level was pinned at the interface states 0.475eV above the valence band.