JP2552058B

This invention is concerned with the production of Schottky barrier gate contacts in MESFET devices. The contact is produced by wet-chemical removal of native oxide in a sealed inert gas ambient and blow-drying the wet-etched surface with the inert gas prior to deposition of gate electrode metal on GaAs by electron beam evaporation in an inert gas ambient. Use of Pt, due to its higher metal work function, as the gate contact metal results in a Schottky barrier height of 0.98 eV for Pt on n-type GaAs. This is considerably higher than the barrier height of conventionally processed TiPtAu contacts (0.78 eV). To lower the sheet resistivity of the gate contact, Pt is preferably used as a multi-layer contact in combination with metals having lower sheet resistivity, with Pt being in direct contact with the n-type GaAs surface. MESFETs fabricated using PtAu bilayer contacts show reverse currents an order of magnitude lower than TiPtAu-contacted companion devices, higher reverse breakdown voltages and much lower gate leakage. The use of this technology of native oxide removal and the PtAu bilayer contact provides a much simpler method of enhancing the barrier height on n-type GaAs than other techniques such as counter-doping the near-surface or inserting an interfacial layer.