Highly stable sputtered NiInW refractory ohmic contact to n-type GaAs

Abstract

Thermally stable low specific resistivity ohmic contact on n-type GaAs is required to fabricate high-speed GaAs integrated circuits. The Nix-In1−x/W (x being either 0.95 or 0.9) contact prepared by magnetron cathodic sputtering is attractive because this contact is expected to be ohmic and thermally stable after rapid thermal annealing. Moreover, the sputter deposition is well suited for refractory metals. The specific resistivity measurements and microstructural analysis were carried out to establish a simple fabrication process which forms an ohmic contact with low specific resistivity. This last parameter was found to be sensitive to the deposition sequence, and the annealing time and temperature. Low specific resistivity of 10−6 Ω cm2 was obtained for Nix-In1−x/W contact annealing at 850 °C for 10 s. This rapid thermal annealing is interesting because simultaneous annealing for contact formation and activation of implanted dopants is possible. The formation of phases during heat treatment stimulates the Schottky to ohmic contact conversion.