Comparison Of Ti/Al/Pt/Au And Ti/Au Ohmic Contacts On N-Type Zncdo

A comparison of Ti/Au and Ti/Al/Pt/Au Ohmic contacts on n-type Zn0.05Cd0.95O layers grown on ZnO buffer layers on GaN/sapphire templates showed a minimum contact resistivity of 2.3x10(-4) Omega cm(2) at 500 degrees C anneal temperature for Ti/Al/Pt/Au and 1.6x10(-4) Omega cm(2) at 450 degrees C for Ti/Al. The morphology of the Ti/Al/Pt/Au contacts showed much better thermal stability and remained smooth until at least 450 degrees C, whereas the Ti/Au contacts show a reacted appearance after 350 degrees C anneals. Auger electron spectroscopy depth profiling of the contact schemes as a function of anneal temperature suggests that the formation of TiOx phases that induce oxygen vacancies in the ZnCdO are responsible for the improved contact resistance after annealing in both types of metal schemes. (c) 2006 American Institute of Physics.