Journal of Applied Physics vol:75 issue:4 pages:2055-2060
The ohmic contact formation mechanism in furnace alloyed Ni/Au/Te/Au/GaAs structures is investigated by the combined application of x-ray diffraction and Raman spectroscopy. It was found that the Ni top layer promotes a more uniform dissociation of the GaAs substrate by the formation of a ternary Ni(x) GaAs phase in the initial stages of contact formation (T= 350-degrees-C). At an alloy temperature T=550-degrees-C, which induces low resistive electrical behavior, the formation of epitaxial Ga2Te3 was observed, indicating the formation of a Ga2Te3/GaAs heterojunction. After alloying at 600-degrees-C, Ga2Te3 Was still found to be present in the contact zone. In addition, evidence for a regrowth of GaAs crystallites could be derived from an increase of the intensity ratio I(TO)/I(LO) of the GaAs Raman signals. No indication for the presence of a high density of shallow donors (> 10(19) cm-3) in the GaAs top layers could be adduced.