Scanning transmission electron microscopy study of Au/Zn/Au/Cr/Au and Au/Ti/Pt/Au/Cr/Au contacts to p-type InGaAs/InP

We studied the interfacial reaction of Au/Zn/Au/Cr/Au and Au/Ti/Pt/Au/Cr/Au contacts to p-InGaAs/p-InP using scanning transmission electron microscopy. We found that the alloying morphology was distinctly different in the two contact systems. For Au/Zn/Au/Cr/Au, significant interdiffusion between the metal and InGaAs contact layer occurred. Two types of compound were formed: one was rich in Au and the other was rich in Ga and As. Another interesting observation was that a significant amount of As has outdiffused into the Cr layer after alloying. For the Au/Ti/Pt/Au/Cr/Au, only interfacial layers were involved in the reaction. Compounds of Au-Ga-In, Ti-As, and Au-Ga were formed, and the Cr layer remained intact. The mechanisms of compound formation are discussed. (C) 2003 American Institute of Physics.