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

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Abstract
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.