Boosting the photodetection of bulk aluminum nitride crystals-based MSM device through an additional electrode

Abstract

Aluminum nitride (AlN) exhibits excellent high-temperature resistance, chemical stability, and a wide bandgap, making it a prime candidate material for deep ultraviolet detectors. In this study, a modified metal–semiconductor–metal (MSM) photodetector using titanium (Ti) electrodes and millimeter-scale AlN bulk polycrystals grown through physical vapor transport is developed, demonstrating photoresponse to light from visible to vacuum ultraviolet. An additional tungsten (W) electrode is designed on the backside of the device, transforming it into a W-MSM device. A proper bias to the W electrode (VW) is found valid to boost the performance of the photodetector. Representatively, with a V of 20 V and VW of −12 V applied, the device achieves improvements in responsivity (R), detectivity (D*), and external quantum efficiency of 112.84%, 30.5%, and 112.84%, respectively, to 532 nm light and 123.18%, 36.84%, and 123.18%, respectively, to 193 nm light. Furthermore, it is found that with the total voltage being instant, optimizing the distribution of voltage between the Ti electrode and the W electrode would induce a better photoresponse than applying voltage solely to the Ti electrode (VW = 0 V). The reason is elaborated through modeling the voltage distribution in the device, revealing the particular role of the bulk semiconductor in this feature. This research provides a facile and innovative approach to developing low-power photodetectors for bulk materials.