Micro structural study of Ti/Pt/Au contacts to p-InGaAs

Reactions that occur at the Ti/InGaAs interface during annealing (≤350°C) of Ti/Pt/Au ohmic contacts to p-type InGaAs have been studied using transmission electron microscopy (TEM). Two different InGaAs surfaces were studied; one given a hydrophobic etch (1% HF) prior to metallization deposition and one oxidized (≈ 3 nm thick) in a UV ozone environment prior to metallization. Qualitatively, the reactions were the same for both types of InGaAs samples, i.e. InGaAs decomposition began at low annealing temperatures resulting in the formation of TiAs, metallic In and Ga-rich InGaAs. Low temperature reactions were enhanced for the UV ozone treated InGaAs surfaces, due to Ti reduction of the oxide layer. Higher temperature annealing did not change the reaction products, only the extent pf reaction. The In that formed had a pyramidal shape and exhibited preferred growth within the InGaAs—the base sides were parallel to InGaAs (110) planes, while the particles protruded into the InGaAs along InGaAs (111) planes.