Comprehensive study of high stability AlN based solar blind MSM photodetectors with Ti/Au contacts

Abstract

Improving the contact quality and improving the surface of aluminum nitride are critical factors in developing high-performance, stable photodetectors. In this study, we investigated the effect of HCl cleaning on the surface oxidation of AlN. X-ray photoelectron spectroscopy analysis confirmed that HCl cleaning significantly reduced the oxide layer compared to cleaning with acetone and isopropyl alcohol alone. Furthermore, after cleaning, the contact resistance between the Ti/Au Ohmic contact and AlN was reduced, enhancing the electrical performance. We applied this process to a metal–semiconductor–metal AlN-based photodetector structure and observed that the photodetector exhibited an acceptable responsivity value at a wavelength of 208 nm with very low light intensity. The responsivity increased with light intensity, reaching 861.52 nA W⁻¹ at 2 μW and 267.72 nA W⁻¹ at 70 μW. The detectivity followed a similar trend, starting at 1.6 × 10¹⁰ Jones at 2 μW and decreasing to 5 × 10⁹ Jones at 70 μW. Additionally, the photodetector demonstrated fast response times, with delay and rise times of approximately 110 ms and 220 ms, respectively under 2 μW light intensity. The impact of temperature on device performance was also investigated, and the photodetector exhibited good stability. Additionally, the effect of cyclic thermal stress on the AlN MSM photodetector was studied between 25 °C and 200 °C. The device demonstrated excellent long-term performance. These results suggest that AlN-based MSM photodetectors, utilizing Ti/Au contacts and HCl cleaning, exhibit not only high performance in terms of responsivity and detectivity but also robust thermal and long-term stability, making them promising candidates for various demanding applications.