Modelling the effects of piezoelectrically active defects and their impact on the threshold voltage of GaAs metal-semiconductor field effect transistors

Abstract

In this paper we discuss the effects of residual structural crystal defects on the threshold voltage V T of GaAs metal-semiconductor field effect transistors via piezoelectric charge distributions set up around individual point defects. This represents a “first-cut” effort to elucidate the piezoelectric impact of defects/dislocations in a GaAs substrate and their subsequent device characteristic alterations. V T shifts ΔV T associated with the edge, screw and 60° types of defects are modelled using a simple one-dimensional calculation of the moment arm of the induced charge distribution. Such calculations are in line with experimental evidence and show for the first time that the piezoelectric impact, even of point defect structures, is significant (i.e. ΔV T of the order of tens of millivolts from an individual defect).