Indium tin oxide (ITO) and Al-doped ZnO (AZO) interfacial layers for Ohmic contacts on n-type Germanium

Abstract

Summary form only given. Recent reports have demonstrated the suitability of ZnO as an interfacial layer for unpinned, low resistance metal-interfacial layer-semiconductor (MIS) contacts on n-Ge from experimental and theoretical standpoints. The doping level in the interfacial layer can significantly impact the contact resistance by controlling the tunnel barrier width. In this work we have compared Al-doped (2%) ZnO (AZO) and Indium tin oxide (ITO, 5% Sn) along with annealed (n+) ZnO interfacial layers reported earlier. All three layers unpin the Fermi level on n-Ge and have nearly similar conduction band offsets (~-0.1 eV). However ITO-based n-Ge contacts exhibit lower thickness dependence and higher current densities as compared to AZO and ZnO, likely due to the higher doping in the ITO layer.