Effect of ohmic contact conductance on the distribution of surface and bulk currents in semiconductor planar devices

Abstract

We investigate the effect of the ohmic contact conductance on the current distribution in the surface and bulk layers in semiconductor planar devices. In particular we analyze the current-voltage characteristics in the three-probe configurations, where probe one is the injecting contact and probes 2 and 3 are the drains. We find that the current distribution is substantially affected by the contact conductance and the ratio between the shunt currents from probes 1 to 2, and from 1 to 3 is mainly dominated by the contact and surface conductivities in the sample. This ratio is less sensitive to the change of the bulk conductivity. We also show the effect of the geometric parameters of the sample on the current distribution. In addition, the lines of current from probes 1 to 2 are concentrated within a thin surface layer. Therefore, the current through probe 2 is determined by the bulk and surface conductances as well as by the contact conductivity. On the other hand, the current through probe 3 is primarily controlled by bulk and contact conductivity. This makes it possible to simultaneously measure surface and bulk conductances in semiconductors if the contact conductivity is known.