Fabrication and Characterization of Photojunction Field-Effect Transistor

In this article, ZnO Quantum Dot (QD)-based photojunction field-effect transistor (photo-JFET) has been fabricated for the detection of ultraviolet (UV) spectrum. The effects of photojunction between the ZnO Quantum Dots (QDs) and deep work function transparent MoO₂ is analyzed under the illumination of UV. The illuminated optical power density acts as a floating gate for the JFET. The device was fabricated on a glass substrate using interdigitated electrodes (Ag) followed by ZnO QDs layer and MoO₂. The dark current between source and drain was found minimum, 2.79 µA/cm², in the case of photojunction as compared to the metal semiconductor metal (MSM)ZnO QDs photoconductor 19.32 µA/cm² at an applied bias of 10 V. The reduction in dark current is attributed due to the effect of the junction formed between ZnO QDs and MoO₂ with the rectification ratio of ~347. The MoO₂ depletes the ZnO QDs channel between the electrodes and reduces the dark current which in turn helps to improved photodetector characteristics.