Abstract: An improved field-effect transistor is provided by forming the conducting channel boundary opposite the gate electrode as a heterojunction. For example a GaAs conducting channel may be bounded by an AlGaAs layer. The conduction electrons can penetrate the boundary very little and are constrained to the channel layer having good transport properties. The output conductance is reduced and the transconductance increased.

Abstract: By positioning the source and gate electrodes on the opposite faces of the active layer, these electrodes can be brought closer together and may have their adjacent edges mutually aligned or even overlapping. The series source resistance and channel resistance can be greatly reduced, because of this closer spacing, which can not be attained when the electrodes are coplanar. By also locating the drain electrode on the same side of the active layer as the source, the source-to-drain spacing can be significantly reduced, reducing channel length and improving the high frequency performance of the transistor. Further, because the electrodes are located on both sides of the active layer, it is possible to provide a large area contact on the bottom, or substrate, side of the epitaxial wafer structure which can advantageously be used to provide a low thermal and electrical resistance connection for the source contact, for example.