Nonalloyed ohmic contact to n-GaAs with GaS/GaAs quasi-metal-insulator-semiconductor structure

We report on nonalloyed ohmic contact to n(+)-GaAs (approximate to 2X10(18) cm(-3)) with a Ti-based metal/ultrathin GaS (approximate to 15 nm)/GaAs quasi-metal-insulator-semiconductor (QMIS) structure. The GaS film was grown by molecular beam epitaxy employing the precursor, tertiarybutyl-galliumsulfide-cubane ([(t-Bu)GaS](4)). For Au/Pt/Ti/GaS/n(+)-GaAs QMIS structure, the as-deposited contact resistivity of low 10(-2) Omega cm(2) was improved to 4.1X10(-6) Omega cm(2) by low-temperature annealing at 300 degrees C for 10 min. With annealing, we observed the formation of TiGaS on GaAs, but did not see any alloying reaction between GaAs and metals and sulfur diffusion into GaAs. (C) 1998 American Institute of Physics. [S0003-6951 (98)03832-7].