TCAD Based Investigation of Junctionless Phototransistor for UVC Radiation Detection

In this study, a gallium oxide gated junctionless phototransistor has been proposed for the first time for deep ultraviolet (210-280 nm) solar blind radiation (UVC) detection. The inherent optical property of gallium oxide has been utilized here to absorb deep ultraviolet radiation. It is designed as a photo absorber layer over the complete channel of the junctionless field effect transistor. Here, the conduction material is silicon (source, channel, and drain), which is entirely separated by the photo absorber (gallium oxide) layer with an intermediate silicon dioxide insulation layer, resulting in MOS-based architecture. The design optimization has been done using the SILVACO ATLAS-2D TCAD simulations by first calibrating the experimentally fabricated junctionless transistor. The study of the proposed gallium oxide gated junctionless phototransistor shows that the gallium oxide thickness of 30 nm is the best-optimized thickness with a maximum responsivity of 4.38 x 104 A/W and detectivity of 1.1 x 1012 Jones achieved at a very less required Vgs =-0.03 V. The spectral response has been performed and it has been calculated that the proposed architecture is best sensitive for 210 nm wavelength and sensitivity reduces significantly outside the deep UV solar spectrum. The time response analysis has also been presented, and it is concluded that the junctionless phototransistor has the advantage of less gate voltage requirements than other gallium oxide-based phototransistors with quite high responsivity in the deep UV solar spectrum.