Thermal Stability of Non-Alloyed Ohmic Contact to n-GaAs

The thermal stability of the non-alloyed GaAs/Pd/Ge ohmic contact to n-GaAs, based on the solid phase epitaxy of Ge on GaAs through PdGe, was investigated at 300°C. Annealings up to 200 hours induced an increase of the contact resistivity from the starting average value of 0.16 Ohm-mm up to 0.30 Ohm-mm. Even though no structural modification was detected by MeV Rutherford Backscattering Spectrometry measurements and Scanning Electron Microscopy observations, cross sectional Transmission Electron Microscopy analyses detected some changes at the PdGe/Ge interface in the long term annealed samples which could induce the formation of a resistive layer between Ge and PdGe.