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

摘要

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 ${sim}{rm 5.1}~{rm nA}/{rm cm}^{2}$ under ${-}{rm 5}~{rm V}$, a high UV/visible rejection ratio of more than $10^{{4}}$, and a zero-bias peak responsivity of ${sim}{rm 0.19}~{rm A}/{rm W}$ 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.