Abstract: The channel region of the FET device has a first portion adjacent the source which has a higher bandgap energy or a higher electron affinity than a remaining portion of the channel. A quasi-electric field in the channel near the source is intensified and as a result, accelerates charge carriers in the channel and increases switching speed. An infrared controlled FET device is also disclosed in which a low bandgap channel layer has a large bandgap layer deposited on it to result in a conduction band discontinuity at the junction between the large bandgap semiconductor layer and the low bandgap channel layer and a two-dimensional electron gas (2DEG) channel in the low bandgap channel layer so that photons reaching the 2DEG eject charges and allow conduction through the channel layer.