Effect of Au overlayer on PtSi ohmic contacts with n-InP

This investigation considers ohmic contact structures Si/Pt/n-InP and Au/Si/Pt/n-InP. The processing conditions achieving low specific contact resistance were derived. Experimental results indicated that the Si/Pt/n-InP showed poor ohmicity; while a low specific contact resistance of 3.32 × 10−5 Ω cm2 was obtained on the Au/Si/Pt/n-InP contact after rapid thermal annealing (RTA) at 550 °C for 30 s. Additionally, the Si/Pt/n-InP contact underwent a sintering reaction. The Au/Si/Pt/n-InP was formed in an alloying reaction and the contact morphology was a little rough after thermal annealing. The ohmicity of the Au/Si/Pt/n-InP contact was attributed to Si doping, and determined by the alloyed reaction and the decomposition of the epitaxial layer of the metallization/InP interface. The Au/Si/Pt/n-InP also exhibited good thermal stability without degradation, with a low maintained specific contact resistance of 2.77 × 10−5 Ω cm2 after 400 °C for 80 h of thermal aging.