Raman Scattering Study of the Au-Ge-Gaas Ohmic Contact Structure Formed by Rapid Thermal Processing

Abstract

ABSTRACTRaman Scattering Was Used To Obtain New Information on the formation of Au-Ge-GaAs alloyed ohmic contacts. During alloying, we observe that amorphous Ge is transfoplmed into polycrystalline material. When Ge diffuses into the GaAs, no n+-GaAs layer is formed. Due to the intermixing of layers, both GaAs and Ge had a large number of impurities which formed deep electronic states in the forbidden gap. Electronic light scattering involving these states was observed. While several models for the Au-Ge-GaAs ohmic contact have been proposed, the model consistent with our Raman data includes resonant tunneling assisted by impurity levels in the graded Au-Ge-GaAs heterojunction structure as a basic conduction mechanism.