Double-injection-induced conductivity between n and p contacts to semi-insulating GaAs

Conductance between ion-implanted, coplanar n and p contacts on nominally undoped semi-insulating (SI) GaAs has been studied. The data reveal a time-dependent double-injection-induced conductance in the SI region between the contacts and an exponential current versus voltage junction conductance. To interpret the data a two-dimensional model is proposed in which current flows in a thin p-like layer near the surface, the conductance of which is modulated by transverse charge separation and consequent electron trapping.