High-temperature isothermal capacitance transient spectroscopy study on SiN deposition damages for low-Mg-doped p-GaN Schottky diodes

Attempt to achieve a surface passivation of p-type GaN was conducted on low-Mg-doped p-GaN by employing SiN films depositions by an Ar-plasma-sputtering and a plasma-enhancement chemical vapor deposition. Process induced damages were then characterized by using a high-temperature isothermal capacitance transient spectroscopy. A large single peak, likely attributed to acceptor-type surface states, was detected in the as-grown samples. The energy level was measured to be 1.18 eV above the valence band edge, which is close to a Ga-vacancy (VGa) reported elsewhere. It was suggested that a small portion of Ga atoms were missing from the surface, and a large density of VGa were created in a few surface layers. The peak intensity was found to significantly decrease by the SiN depositions, irrespective of the deposition methods, and further decreases upon annealing at 800 °C. After the SiN deposition and the annealing, the peak intensity decreased: the pure Ga vacancies may transform into complex defects in the course of the SiN deposition and annealing. These results show that the present characterization method with the low-Mg-doped p-GaN Schottky contacts is effective and serves as sensitive characterization of the surface defects.