High Quantum Efficiency GaN-Based p-i-n Ultraviolet Photodetectors Prepared on Patterned Sapphire Substrates

In this letter, GaN-based p-i-n ultraviolet (UV) photodetectors (PDs) are fabricated on patterned sapphire substrate (PSS) for the first time. Based on cathodoluminescence mapping and x-ray diffraction measurement, the as-grown structure on PSS has considerably lower defect density than that of a similar structure grown on standard sapphire substrate (SSS). The PD on PSS exhibits a low dark current density of ~ 5.1 nA/cm2under -5 V, a high UV/visible rejection ratio of more than 104, and a zero-bias peak responsivity of ~0.19A/W at 360 nm, which corresponds to a maximum quantum efficiency of 65%. In the photo-sensitive wavelength region between 250 and 365 nm, the quantum efficiency of the PD on PSS is, on average, over 30% higher than that of the control device fabricated on SSS.