Optimization of All Figure-of-Merits in Well-Aligned GaN Microwire Array Based Schottky UV Photodetectors by Si Doping

GaN nano/microwires, due to their large surface-to-volume ratio and the reduced dimensionality, have been widely used in high-performance ultraviolet (UV) photodetectors (PDs). However, there has been a fundamental trade-off between the photocurrent gain and the speeds of PDs, which have limited their practical applications. In this work, highly ordered GaN microwire array based Schottky UV PDs have been fabricated, and optimizing Si doping concentrations can entirely improve the performances of the devices. The results show that output photocurrent increases monotonously as increasing doping concentration, while the dark current experiences a decrease followed by an increase, resulting in an optimized value under a certain doping concentration. At doping concentration of 1 × 1018 cm–3 with 2.2 mW cm–2 illuminating intensity, the sensitivity, responsivity, and detectivity of the devices are greatly enhanced by 1.84 × 104%, 163%, and 2103%, respectively. Meanwhile, the time-dependent response in Si-doped device possesses fast response time (τon < 10 ms and τoff < 10 ms) at this optimum concentration, compared with that of undoped one (τon = 70 ms and τoff = 90 ms). The effective advances in the devices are attributed to the increased Schottky barrier height by Si doping and the intensive oxygen molecules adsorption and desorption processes in microwire surface. This study offers a design guideline for the optimum doping concentration for obtaining high performances in microwire-based PDs.