Thermal stability of Pt/doping element/Pd ohmic contacts to GaAs

The thermal stability of Pt/doping element/Pd ohmic contacts with Ge, Si and Sn in the position of doping elements was investigated. Three sets of metallization differentiated by the thickness of particular layers were prepared with help of high vacuum evaporation or sputtering. The Pt(50 nm)/Pt(50 nm)/Si(40 nm)/Pd(10 nm) metallization deposited by sputtering shows the best stability. The changes in the contact resistivity in the process of ageing are not due to phase transformations at the semiconductor-metallization interface, but are probably caused by the doping element-GaAs interdiffusion.