Study of titanium tungsten nitride and tungsten nitride Schottky contacts on n-GaN

The Schottky diode behaviors of the TiWNx and the WNx Schottky contacts to n-GaN were investigated at different annealing temperatures. Both TiWNx and WNx films were deposited by the reactive DC sputtering method. The WNx/n-GaN contact exhibited excellent electrical characteristics even after rapid-thermal annealing up to 850degreesC for 10s. The ideality factor and barrier height remained 1.09 and 0.8OeV, respectively, after 850degreesC annealing. However, the TiWNx/n-GaN contact was thermally stable only up to 650degreesC annealing; the values of the ideality factor and the barrier height were 1.14 and 0.76 eV, respectively, after 650degreesC annealing and started to degrade when annealed at higher temperatures. The deterioration of the TiWNx/n-GaN contact at higher temperatures was due to the inter-diffusion of the TiWN film and the GaN material.