Thermally Stable And Low-resistance W/ti/au Contacts To N-type Gan

摘要

We report on the formation of thermally stable and low-resistance Ti/Au-based ohmic contacts to n-type GaN (4.0 × 10~(18) cm~(-3)) by using a W barrier layer. It is shown that the electrical characteristic of the sample is considerably improved upon annealing at 900 ℃ for 1 min in a N_2 ambient. The contacts produce the specific contact resistance as low as 6.7 × 10~(-6) Ω cm~2 after annealing. The Norde and current-voltage methods are used to determine the effective Schottky barrier heights (SBHs). It is shown that annealing results in a reduction in the SBHs as compared to that of the as-deposited sample. Auger electron spectroscopy (AES), scanning transmission electronrnmicroscopy (STEM) and X-ray diffraction (XRD) examinations show that nitride and gallide phases are formed at the contact/GaN interface. Based on the AES, STEM and XRD results, a possible ohmic formation mechanism is described and discussed.