Annealing and measurement temperature dependence of W2B5-based rectifying contacts to n-GaN

The thermal stability and measurement temperature dependence of Schottky contact characteristics on n-GaN using aW2B5/ Ti/Au metallization scheme was studied using current–voltage (I–V), scanning electron microscopy (SEM) and Auger electron spectroscopy (AES) measurements. The elemental profile obtained from samples annealed at 350 8C showed some titanium diffusion into the gold layer but little other difference from the as-deposited wafer. Annealing at 700 8C produced significant diffusion of titanium. The Schottky barrier height increased with anneal temperature up to 200 8C, reaching a maximum value of 0.65 eV, but decreased at higher annealing temperatures. The reverse breakdown voltage from diodes fabricated using theW2B5- based contacts showed a similar dependence. The reverse current magnitude was larger than predicted by thermionic emission alone. The barrier height showed only minor changes with measurement temperature up to 150 8C.