Effect of Frost Formation on Operation of GaN Ultraviolet Photodetectors at Low Temperatures

Effects of frost growth on the sensitivity of gallium nitride (GaN) photodetectors were investigated by characterizing electrical and optical properties under dark and 365-nm ultraviolet (UV) illumination from room temperature down to -100°C. The direct wire bonding architecture was used to create aluminum/GaN interdigitated devices for the microfabrication. As the operation temperature decreased below -5°C, the frost formed from humid air was observed on the GaN surface, and photo-to-dark current ratio (sensitivity factor) showed significant reduction (6.76 at room temperature and 2.73 at -100°C under 1 V-bias). The presence of frost on the device surface significantly reduced the absorption of incident UV light into the GaN surfaces (average 85.6% reduction from room temperature to -70°C). This paper supports the characterization of the GaN for UV detection within low-temperature environments, such as cryostats, Arctic research, and space exploration applications.