High performance FET devices

A field effect transistor (FET) with an epitaxially layered structure comprising:

• a single crystal substrate of a selected conductivity type, the selected conductivity type being either n-type or p-type;
• a first semiconductor layer on the substrate, or on a buffer layer between the substrate and the first semiconductor layer, the first semiconductor layer being of the same conductivity type as that of the substrate or the buffer layer;
• a second, active semiconductor layer on the first semiconductor layer, the conductivity type of the second, active layer being opposite that of the first semiconductor layer;
• wherein at least one of the first or second semiconductor layers contains zinc oxide or an alloy of zinc oxide;
• two electrical contacts on the second semiconductor layer to form respectively a source contact and a drain contact;
• a gate contact on the second semiconductor layer located between the source contact and the drain contact to form an active channel layer;
• an electrical contact formed on a selected one of the substrate, the buffer layer or the first semiconductor layer;
• and
• a gate voltage bias supply circuit element operable to be connected to (1) the electrical contact formed on a selected one of the substrate, the buffer layer or the first semiconductor layer, and (2) the gate contact, with polarity and magnitude sufficient to increase the high frequency response and operational performance of the FET.