Low resistance WSix-based ohmic contacts on n-type GaN

Low contact resistance, high reflectivity, and high thermal stability Ti∕WSix∕Ti∕Au multilayer ohmic contact to n-type GaN has been demonstrated. Specific contact resistivity as low as 1×10−6Ωcm2 is obtained in a metallization scheme of Ti∕WSi0.05∕Ti∕Au (20∕40∕20∕200nm) after thermal annealing at 800°C for 3min in N2 ambient. Its specific contact resistivity maintains at the same level after heat treatment at 300°C for 96h. In addition, the optical reflectivity in the wavelength range of 350–450nm is about twofold higher than that of the conventional Ti∕Al∕Ti∕Au (30∕100∕40∕120nm) contact. The former also exhibits much smoother surface and better edge acuity, which is essential for devices sensitive to critical dimension control.