Conductance statistics of small-area ohmic contacts on GaAs

The conductance distributions of very small-area alloyed ohmic contacts on n+-GaAs have been studied as a function of lateral contact size d, with d ranging from 4 μm down to 0.3 μm. The data are fairly well represented by a Poisson distribution, which takes into account the granularity of the alloyed contacts, as previously reported. We deduce an average distance of dc ≃0.41 μm between conducting grains and a dead zone of ld ≃600 Å due to dry etching of the GaAs.