Vincent Leo Rideout

A review of the theory and technology for ohmic contacts to group III–V compound semiconductors

Abstract The technology for ohmic contacts to group III–V compound semiconductors is reviewed in this paper. The basic principles of current transport in metal-semiconductor (Schottky barrier) contacts are presented first. The modes of current transport considered are thermionic emission over the barrier, and tunneling through the barrier due to thermionic-field or field emission. Special attention is devoted to the parameters of temperature and doping concentration which determine the dominant mode of conduction. As the primary mode of conduction changes from thermionic emission dominated to tunneling dominated, the current-voltage behavior of the contact changes from rectifying to ohmic in character. The experimental techniques for fabricating ohmic contacts to III–V compound semiconductors are then described. Contact problems as they pertain to specific device applications are considered. Finally, present difficulties with contacts to mixed III–V crystals are discussed.

GaAsGaAlAs heterojunction transistor for high frequency operation

Abstract A bipolar transistor structure is proposed having application for either high frequency operation or integration with certain types of light emitting devices. The structure involves liquid phase epitaxially grown layers of GaAs for the collector and base regions, and of Ga1−xAlxAs for the heterojunction emitter. The high frequency potential of this device results primarily from the high electron mobility in GaAs and the ability to heavily dope the base region with slowly diffusing acceptors. The Ga1−xAlxAs emitter region provides a favorable injection efficiency and, because it is etched preferentially relative to GaAs, access to the base layer for making contact. Transistor action with d.c. common emitter current gains of 25 have been thus for observed. Calculations of the high speed capability of this transistor are presented.