Indium-based ohmic contacts to n-GaAs, fabricated using an ion-assisted deposition technique

The effect of simultaneously depositing In metallization on n-GaAs using a novel ion-assisted deposition (IAD) technique has been investigated. Using current-voltage, specific contact resistance and secondary ion mass spectroscopy measurements, the contacts were compared to conventional contacts fabricated using thermal evaporation. Ion-mixed contacts fabricated with an ion dose of 2.8 × 1018 ion cm-2 and ion energy of 1 keV exhibited a lower specific contact resistance of 3 × 10-6 cm-2 at a lower annealing temperature of 375 °C compared to conventionally fabricated contacts. For all ion doses the annealing time and temperature which gave the minimum specific contact resistance remained unchanged. SIMS analysis also confirmed that the In deposited using the ion deposition technique formed a graded junction prior to annealing. After annealing both ion-mixed and thermally evaporated contacts had formed the graded junction and were electrically comparable.