Comparison of Ti/Al/Pt/Au and Ti/Au Ohmic contacts on n-type ZnCdO

摘要

A comparison of Ti/Au and Ti/Al/Pt/Au Ohmic contacts on n-type Zn_(0.05)Cd_(0.95)O layers grown on ZnO buffer layers on GaN/sapphire templates showed a minimum contact resistivity of 2.3 X 10~(-4) Ω cm~2 at 500℃ anneal temperature for Ti/Al/Pt/Au and 1.6 X 10~(-4) Ω cm~2 at 450℃ for Ti/Al. The morphology of the Ti/Al/Pt/Au contacts showed much better thermal stability and remained smooth until at least 450℃, whereas the Ti/Au contacts show a reacted appearance after 350℃ anneals. Auger electron spectroscopy depth profiling of the contact schemes as a function of anneal temperature suggests that the formation of TiO_x phases that induce oxygen vacancies in the ZnCdO are responsible for the improved contact resistance after annealing in both types of metal schemes.