On the rectifying ability of a p-type semi-insulating junction

Abstract

The system consisting of an unintentionally doped GaAs epitaxial layer on a semi-insulating (SI) GaAs substrate forms a starting point for the GaAs integrated circuit technology. It is also the genesis of problems for GaAs field-effect transistors (FETs) in the form of back gating. Potentials applied to a point on the surface may propagate several millimeters to modulate the conduction of an FET built into the layer. In addition, the conductivity of the epilayer may be efficiently modulated by a potential applied to the back of the SI substrate. Well-developed p-channel FET characteristics have been observed in an epilayer on top of a 0.4-mm-thick SI substrate using the back of the substrate as a gate. Numerical simulations revealed that under some circumstances potentials may propagate across the substrate with little attenuation, giving a degree of modulation in agreement with experiment. Conditions for current transport then corresponded closely to those in a rectifying p-n junction. The parameter space was fully explored numerically and using an analytical model, and a simple set of conditions for rectification were developed.