Thermally stable, low-resistance NiInW ohmic contacts to n-type GaAs

A new thermally stable, low-resistance NiInW contact metal to n-type GaAs has been developed by depositing a thin In layer with Ni and W layers and annealing at elevated temperatures for a short time. Low resistances of ∼0.3 Ω mm were obtained at annealing temperatures in the range of 800 to 1000°C. The contact resistances were stable during subsequent annealings at 400°C for 100 h and 500°C for 10 h. The thermal stability of the contact resistance and the surface morphology of this contact are superior to those of the conventionally used AuNiGe contacts and this new contact is suitable for various device applications. Further reduction of the contact resistance can be achieved simply by reducing the sheet resistance of the contact metals.