A MOSFET-Like Infrared Sensor for the Enhancement of Photoconductivity and Photoresponsivity

In this study, a metal oxide semiconductor field effect transistor (MOSFET)-like infrared (IR) sensing method is presented. The orderly uneven barrier-layer surface of an anodic aluminum oxide (AAO) membrane was used as the substrate. The thickness of the barrier-layer was reduced by phosphoric acid etching following which a microchannel was transferred to the barrier-layer by the photolithographic technique. Single walled carbon nanotubes (SWNTs) were deposited into the microchannel as the sensing element. A gold thin film that served as the gate electrode was sputtered on the opposite side of the barrier-layer of the AAO substrate. A thin layer of polydimethylsiloxane (PDMS) was then cast on the SWNTs to insulate them from the surrounding ambiance. A thin film of indium tin oxide (ITO) was sputtered onto the PDMS layer to act as the counter electrode for the gate electrode. The conductance of the sensing element could be better controlled by the width of the microchannel and the amount of the deposited SWNTs. Experiments demonstrated that the proposed MOSFET-like IR sensor could effectively sense IR signals in the air at room temperature under a very weak power intensity (17 μW/cm2) of IR illumination and an 0.01 V applied drain-source voltage. A 0.5 sec photocurrent response time and a 2.4% of conductivity enhancement were measured.