Thermally stable, low-resistance NiInWNx ohmic contacts to n-type GaAs prepared by sputter deposition

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Abstract
A new thermally stable, low‐resistance In‐based ohmic contact to n‐type GaAs has been developed. The contacts consist of ion‐beam sputtered Ni (5 nm)/In (5 nm)/Ni (5 nm) layers with a magnetron sputtered WNx overlayer. A low‐contact resistance of ∼0.3 Ω mm was obtained by rapid thermal annealing at 750 °C for ∼5 s. The contact resistance and the excellent contact morphology remained unchanged after annealing at 400 °C for more than 100 h. The present deposition technique provides several advantages over previously reported electron‐beam evaporated In‐based contacts. In particular, the ability to deposit a thick WNx overlayer simplifies GaAs integrated circuit (IC) fabrication by (a) eliminating the need for separate diffusion barrier deposition and patterning steps, and (b) providing for low‐sheet resistance (∼2 Ω/⧠) IC interconnect capabilities. In addition, sputter deposition allows for the controlled incorporation of n‐type dopants into the metallization if further reduction of the contact resistance is required.