Heterostructure transistor using real-space electron transfer

Abstract

A charge injection transistor is a real-space electron transfer heterostructure with several novel features. The channel layer is comprised of In.sub.0.25 Ga.sub.0.75 As supported by a buffer layer of Al.sub.0.3 Ga.sub.0.7 As resting on the substrate. A barrier layer comprised of Al.sub.0.1 Ga.sub.0.9 As overlays the channel layer. Over this barrier is a layer of GaAs forming the electron drift region. The collector electrode is located on top of this drift layer, between the source and heater electrodes, which extend downward through the drift and barrier layers and create the electric field in the channel layer. Positive voltages are applied to the heater and collector, relative to the source. Electrons flow through the channel region and become heated. At sufficiently high temperature they escape over the barrier and travel through the drift region to the collector. In comparison with previous devices, the use of InGaAs in the channel layer provides a deeper quantum well for the conduction electrons, and suppresses leakage through the barrier at room temperatures. The collector drift layer has a short transit time delay. The location of the collector reduces parasitic leakage from the source, and the collector capacitance is small. These features enhance the high frequency performance of the device. The limiting power gain frequency and current gain frequency are at least twice the corresponding values attained in previous devices.