Film thickness degradation of Au/GaN Schottky contact characteristics

Electrical characteristics of Au/n-GaN Schottky contacts with different Au film thicknesses up to 1300 Å, have been investigated using current–voltage (I–V) and capacitance–voltage (C–V) techniques. Results show a steady decrease in the quality of the Schottky diodes for increasing Au film thickness. I–V measurements indicate that thin (<500 Å) film Schottky diodes show significantly better rectification characteristics than those of thick Au films (>500 Å). Depth profiling Auger electron spectroscopy (AES) shows that the width of the Au/GaN junction interface increases with increasing Au thickness, suggesting considerable inter-mixing of Au, Ga and N. The results have been interpreted in terms of Ga out-diffusion from the GaN giving rise to gallium vacancies that in turn act as sites for electron–hole pair generation within the depletion region. The study supports the recent suggestion that gallium vacancies associated with threaded dislocations are playing an important role in junction breakdown.