NiAl/n-GaAs Schottky diodes: Barrier height enhancement by high-temperature annealing

A metallurgically stable and laterally uniform contact to n-GaAs with an enhanced barrier height (0.99 V) and an ideality factor of 1.10 has been achieved with a NiAl bimetallic metallization. This barrier height, as measured by the forward current-voltage technique after annealing for 20 s at 650 °C, is higher than the reported barrier heights of refractory metallizations to n-GaAs. Auger electron spectroscopy (AES) sputter profiles reveal an Al-Ga exchange reaction after high-temperature (500–950 °C) rapid thermal annealing. From these results, the barrier height enhancement is attributed to the formation of an Al1−xGaxAs layer at the NiAl/n-GaAs interface. The thermal stability and low electrical resistivity of the NiAl phase, the enhanced barrier height on n-GaAs, and the ease of patterning the as-deposited Ni/Al/Ni layered structure by lift-off techniques make NiAl a very promising gate contact material for GaAs metal-semiconductor field-effect transistors and related devices.