Influence of trap level on an Al0.6Ga0.4N/Al0.5Ga0.5N metal—semiconductor—metal UV photodetector

The irradiation intensity and temperature characteristics of each response speed sample are measured to clarify the high photosensitivity mechanism in an Al 0.6 Ga 0.4 N/Al 0.5 Ga 0.5 N metal–semiconductor–metal photodetector. A tradeoff relation could be observed between the photosensitivity and response speed when the dependence of the saturated photocurrent on the irradiation intensity was investigated by changing the irradiation intensity from 1 nW cm −2  to 45  μ W cm −2 . The rise time of the photocurrent after exposure to ultraviolet light was measured to determine the trap level density that was estimated to be ca. 10 12  cm −2 . Further, the decay time constant was obtained by investigating the dependence of the photocurrent decay time on temperature (25 °C–180 °C). By analyzing the Arrhenius plot of the decay time constant versus inverse temperature, trap level depths of 0.23 and 0.67 eV were obtained. Thus, the high photosensitivity in the Al 0.6 Ga 0.4 N/Al 0.5 Ga 0.5 N photodetector can be attributed to the carriers trapped in deep-level traps.