Investigation of microstructural and electrical properties of self-aligned ni-ingaas alloy contacts to ingaas as a function of rapid thermal annealing temperature

We have investigated microstructural and electrical properties of self-aligned Ni-InGaAs alloy used as contact material to InGaAs as a function rapid thermal annealing (RTA) temperature. The Ni-InGaAs alloy was the only phase resulting from solid-state reaction between Ni and InGaAs, regardless of the RTA temperature. Microstructural evolutions of Ni-InGaAs and overlaid Ni films were observed for increasing RTA temperature. The increase in RTA temperature resulted in increasing the size of the pinholes formed in the Ni film, which could be associated with the columnar growth nature of sputter-deposited Ni film. A relatively uniform Ni-InGaAs layer was formed after RTA at 300^oC, which could be responsible for the minimum specific contact resistivity observed at this temperature. Above this temperature, the Ni-InGaAs layer underwent severe structural degradation such as the formation of microvoids in its surface area, leading to a rapid increase in specific contact resistivity.