The Ge/Pd/n-GaAs Ohmic Contact Interface Studied by Backside Raman Spectroscopy

Abstract

ABSTRACTThe Ge/Pd/n-GaAs ohmic contact structure constitutes a near-ideal model system to test the applicability of the different metal/GaAs ohmic contact models. After annealing, an atomically flat interface between the GaAs substrate and a regrown Ge layer is obtained. A main point of discussion is whether the ohmic conduction across this junction either occurs by an enhanced Ge-doping of the GaAs (regrown) substrate surface layers (the doping model), and/or by a degenerate As-doping ot the Ge overlayer (the heterojunction hypothesis). In order to examine the applicability of both models, a Raman study of this system is undertaken. By a backside thinning procedure, a metallization/60 nm GaAs structure is preserved, allowing for a backside optical analysis of the regrown Ge/GaAs interface region.