Low dark current and high dynamic range a-Si:H MSM photodetector for large area medical imaging

Abstract

ABSTRACT Metal -Semiconductor -Metal (MSM) photodetectors are attractive as sensors due to their ease of fabrication and compatibility with thin film transistor fabrication process primarily because there is no P + doped layer. W e report an a -S i:H MSM lateral structure with low dark current, high dynamic range and comparable sensitivity to conventional p -i-n photodiodes. These improvements are achieved by the introduction of a thin polymer layer as a blocking contact. The fabricated amor phous silicon based MSM detector exhibits a photo -response of more than 3 orders of magnitude to a JUHHQOLJKWVRXUFH QP with intensity of 73µW/cm 2 . In comparison to vertical p -i-n structures, the reported MSM lateral devices show gains in terms o f dynamic range, ease of fabrication (no p+ layer) , and faster speed at the cost of slightly reduced responsivity . The experimental results of dark and photocurrent measurements as well as the responsivity for two in -house fabricated MSM structures at diff erent bias voltages and light intensity are presented. This results are promising and encourage the development of a -Si:H lateral MSM devices for indirect conversion large area medical imaging applications and especially low cost flat panel computed tomogr aphy. Keywords: MSM photodetectors ± Amorphous Si ± indirect conversion X -ray imaging ± dark current