Microstructural and phase evolutions of Pt contact to N-type In0.53Ga0.47As driven by rapid thermal annealing and its correlation with specific contact resistivity

In this study, the microstructural and electrical characteristics of Pt contacts to n-type InGaAs were investigated as a function of rapid thermal annealing (RTA) temperatures in the range of 400–600 °C. RTA at 400 °C was inadequate for ensuring a good reaction between the deposited Pt films with InGaAs, forming only a thin amorphous PtAs2 layer, as evidenced from the high-resolution transmission electron microscope and energy dispersive X-ray spectrometer results. A significant reaction occurred upon RTA at 500 °C, leading to the formation of a PtAs2 phase with most of the Pt being unreactive, but with a reduction in the Pt lattice dimensions. With a smaller atomic radius than Pt, the accommodation of Ga and In atoms in a substitutional solid solution could be responsible for the reduction in the Pt lattice. The reaction between the Pt films and InGaAs after annealing at 600 °C resulted in complete consumption of the Pt films, forming PtIn2, Pt13In9, Pt2Ga3, and Pt5Ga3 phases along with the additional PtAs2 phase as clearly distinguishable layers. The minimum value of specific contact resistivity obtained with RTA at 600 °C could be associated with the metallic PtIn2 in combination with the Pt13In9 alloy embedded in the PtAs2 layer, which serves as a good carrier path.