Abstract
Due to the dislocation that resulted from the lattice mismatch between GaN and sapphire substrate, patterned sapphire substrate (PSS) was widely used in MOCVD epitaxy to improve the crystalline quality instead of conventional sapphire substrate (CSS). We compared PIN devices fabricated on FSS with those on PSS to investigate how dislocation affects the devices characteristics, such as forward turn-on voltage, reverse leakage current and breakdown voltage. Following electrical measurement including current-voltage, capacitance-voltage, and deep-level transient spectroscopy (DLTS) were applied in this study. Besides, edge effect that resulted from side-wall damage during ICP process is an issue in vertical PIN diodes. To overcome this, SiO2 deposition layer was utilized as side-wall passivation to reduce edge effect. Therefore, we also investigate the breakdown characteristics of diodes to realize the influence of passivation layer.