Annealed indium oxide transparent ohmic contacts to GaAs

The current–voltage characteristics of annealed In2O3–GaAs devices have been investigated for the purpose of fabricating transparent ohmic contacts to GaAs. A detailed study of the reverse current for as-deposited structures with degenerately doped n-type In2O3 on lightly doped n-type GaAs yields a 0.67-V high Schottky barrier. After annealing, the barrier height is only slightly modified, but the reverse current increases dramatically. This reverse current follows a voltage dependence that is consistent with a Fowler–Nordheim tunneling mechanism, for which the electric field is enhanced around localized asperities. These data suggest that an optimized annealing schedule might be used to fabricate low-resistance, transparent In2O3 ohmic contacts to GaAs-based optoelectronic devices.