Contacts on n-type germanium using variably doped zinc oxide and highly doped indium tin oxide interfacial layers

摘要

The impact of varying interfacial layer (IL) doping on the performance of Ti/IL-Ge contacts is demonstrated using undoped ZnO, aluminum-doped ZnO (AZO), and O-vacancy-doped n~+-ZnO ILs having similar conduction band offsets △E_o with respect to Ti and Ge. Diode and transfer length method measurements show Fermi-level unpinning for all the ILs; however, the contact resistance and its dependence on the IL thickness decrease with Increasing IL doping owing to the reduction in the tunneling resistance. The contact resistivity depends on the IL doping (N_(IL)) as ρ_(c-n~+-ZnO) ＜ ρ_(c-AZO) ＜ ρ_(c-ZnO) for N_(n~+-ZnO) ＞ N_(AZO) ＞ N_(ZnO). Contacts using a highly doped, low △E_o tin-doped In_2O_3 IL exhibit the lowest value, 1.4 × 10~(-7) Ω·cm~2.