Room-temperature long-wave infrared detector with thin double layers of amorphous germanium and amorphous silicon.

A longwave-infrared photodetector made of double layers of 100nm amorphous germanium (a-Ge) and 25nm amorphous silicon (a-Si) have been demonstrated. Under room temperature, the device shows the responsivity of 1.7 A/W, detectivity of 6x10(8) Jones, and noise equivalent power (NEP) of 5pW/root Hz under 5V bias and at 20kHz operation. Studies of frequency dependent characteristics and device modeling indicate that, above 100Hz or beyond the bandwidth of thermal response, the device operates as a quantum detector having the photoelectrons produced by optical excitation from the bandtail states to the mobile states of a-Ge. The superior device performance may be attributed to the combination of two amplification mechanisms: photoconductive gain in a-Ge and cycling excitation process (CEP) in a-Si, with the latter being the dominant factor. Besides its attractive performance, the device has a simple structure and is easy to fabricate at low cost, thus holding promise for night vision, sensing, autonomous driving, and many other applications. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement