Characterization of alloyed AuGe/Ni/Au ohmic contacts to n-doped GaAs by measurement of transfer length and under the contact sheet resistance

Abstract

The results of systematic measurements of transfer length L/sub T/ and sheet resistance under the contact R/sub sk/ for alloyed AuGe/Ni/Au ohmic contacts to GaAs active layers prepared both by VPE (vapor-phase epitaxy) and by direct selective ion implantation are given. The end resistance measurement technique was used. Also reported are the more commonly measured specific interfacial resistance rho /sub c/ and unit-width resistance r/sub c/. L/sub T/ was relatively constant at 1.35 mu m. A wide range for R/sub sk/ was observed, including values both higher and lower than the pre-alloyed value. It correlates with rho /sub c/ and r/sub c/ and demonstrates that variation in the GaAs/contact interface is the source of the commonly observed wide scatter in these parameters.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>