Thermal stability of tungsten and tungsten nitride Schottky contacts to AlGaN/GaN

Thin tungsten nitride (WN_x) films were produced by reactive DC magnetron sputtering of tungsten in an Ar-N₂ gas mixture. The films were used as Schottky contacts on AlGaN/GaN heterostructures. The Schottky behaviours of WN_x contact was investigated under various annealing conditions by current-voltage (I-V) measurements. The results show that the gate leakage current was reduced to 10^-6 A/cm² when the N₂ flow is 400 mL/min. The results also show that the WN_x contact improved the thermal stability of Schottky contacts. Finally, the current transport mechanism in WN_x/AlGaN/GaN Schottky diodes has been investigated by means of I-V characterisation technique at various temperatures between 300 K and 523 K. A TE model with a Gaussian distribution of Schottky barrier heights (SBHs) is thought to be responsible for the electrical behaviour at temperatures lower than 523 K.