Tellurium doped a-Se devices for improved optical absorption in indirect X-ray photodetection

Amorphous selenium (a-Se) is a high gain, low dark current, large area compatible photoconductor that has received significant attention towards the development of UV and X-ray detectors for medical imaging Indirect detectors utilizing a-Se often feature blue emitting scintillators due to the high attenuation coefficient of a-Se in that region. However, emission tails from the scintillators often fall out of the conversion range of a-Se, and scintillators with emission peaks outside the absorption of Se cannot be utilized In order to improve the sensitivity and gain in a-Se indirect detectors, we propose doping a-Se with tellurium as a function of depth, where tail emission will be absorbed by the lower bandgap a-Se/Te after primary absorption in the initial Se layer. In addition, we employ a lateral device structure to avoid any absorption at short wavelengths from a transparent electrode or blocking layer. In this work, we present the first steps towards fabricating these devices. Studies of charge transport in doped a-Se/Te devices are performed using the transient photocurrent time-of-flight technique. We report hole and electron mobilities for a-Se1-x,Te-x (x = 0, 0.01, 0.05, 0.10) as a function of applied voltage, along with band gaps and comparisons to previous studies. Fabrication of lateral devices, with and without optical slits, is demonstrated and discussed.

Automated summary

This paper presents the initial steps towards improving the sensitivity and gain of a-Se indirect detectors by doping a-Se with tellurium and using a lateral device structure. The charge transport in doped a-Se/Te devices is studied using the transient photocurrent time-of-flight technique.