Schottky barrier enhancement in Ni/Al layer-by-layer contacts to n-GaAs

Electron-beam deposited Ni/Al bimetallic, Ni and Al single-metallic contacts to chemically etched <100> oriented n-type GaAs were studied. These samples were electrically characterized to determine the barrier heights, ideality factors, and doping concentrations. Barrier heights determined from I-V measurements using thermionic emission model yielded larger ideality factors, indicating that thermionic field emission model is more applicable for these contacts. The discrepancies in the barrier height data from I-V and C-V measurements are explained. Chemical analysis using an Auger electron spectrometer showed contamination at the interfaces of annealed samples. The results on single metallic contacts agreed quite well with published data. The authors show the importance of the bimetallic contacts by comparing the electrical properties of Ni/Al Schottky contacts with those made by Ni or Al alone under similar fabrication and processing conditions