The structure and thermal stability of tungsten-based contact metallizations to n-GaN

Thermally stable contacts to n-GaN have been obtained using W and WSi. Low specific contact resistance was achieved for the W metallization with limited reaction between the metal and semiconductor up to 1000°C. The formation of the β-W₂N and W-N interfacial phases were deemed responsible for the electrical integrity observed at these annealing temperatures. The W_x-N_1-x interfacial phases functioned as efficient barriers to the outdiffusion of Ga. For WSi, the β-W₂N interfacial phase formation was observed after annealing at 700° and 800°C. This phase also prevented Ga outdiffusion at these elevated temperatures. Optimization of this phase and moderate suppression of interfacial irregularities occurred after annealing at 800°C. This investigation demonstrates that both W and WSi contacts appear to be reasonable contact choices for high-temperature electronics applications.