Effects of interface reactions on electrical characteristics of metal-GaAs contacts

Solid-state interface reactions between metal thin films and (100) GaAs substrates at elevated temperatures are studied by conventional and heavy-ion Rutherford backscattering spectrometry, x-ray diffraction, and transmission electron microscopy. Metals investigated in this study include Pt, Pd, Ni, Co, Rh, and W. Electrical properties of the metal/n-GaAs diodes undergoing annealing treatments at various temperatures were also measured with the current-voltage dependence. Optimum diodes with maximum barrier heights as well as minimum leakage currents are obtained for diodes annealed at temperatures at which a uniform thin layer of reacted phase is observable at the interface. The barrier heights of the optimum diodes show a linear dependence on the work functions of the various metals. The range of these barrier heights is limited by nonstoichiometry related defects as suggested by a recently proposed amphoteric native defect model.