Fast Lateral Amorphous-Selenium Metal–Semiconductor–Metal Photodetector With High Blue-to-Ultraviolet Responsivity

A lateral metal–semiconductor–metal (MSM) photodetector with a layer of thin amorphous selenium (a-Se) is investigated to detect visible photons. A comparative study on detectors with different a-Se thicknesses is conducted. The thinner detector tends to have better optoelectronic performance, having a low dark current in the range of 40–180 fA under various lateral biases over 1000 s, high responsivity up to $\sim$ 0.45 A/W toward a short wavelength of 468 nm, and high speed of photoresponse up to 2 kHz with signal rise time of 50 $\mu\hbox {s}$ and fall time of 60 $\mu\hbox {s}$ . The fast lateral a-Se MSM photodetector thus has enormous potential to be used in a variety of optical sensing applications, particularly in large-area digital indirect-conversion X-ray imaging.