Thermally Stable Novel Metal Contacts on Bulk, Single-Crystal n-type ZnO

The contact characteristics on bulk single-crystal n-type ZnO of TiB2/Pt/Au, ZrB2/Pt/Au and Ir/Au metallization schemes deposited by sputtering are reported as a function of annealing temperature in the range 200-1000{degree sign}C (N2 ambient). Boride contacts exhibited Ohmic behavior with minimum specific contact resistance between 10-3 and 10-5 Ωcm2 after a 700{degree sign}C or above anneal. The contacts transition to rectifying behavior after annealing above 900{degree sign}C, coincident with a degraded surface morphology. Ir contacts exhibit higher thermal stability than both Boride contacts investigated, exhibiting a minimum specific contact resistance of 3.6x10-6 Ωcm2 after annealing at 1000{degree sign}C. Ir contacts showed very little change in resistance after extended aging (30 days) at 350{degree sign}C.