Numerical Investigation of a New GeSn MIR Phototransistor based on IGZO TFT Platform

In this paper, a new Mid-Infrared phototransistor (MIR PT) design based on InGaZnO (IGZO) thin-film (TF) and GeSn sensitive layer is proposed. Exhaustive study of the device photosensing properties is carried out using accurate numerical models based on FDTD technique. It is revealed that the proposed PT structure can provide enhanced responsivity with reduced dark current. Importantly, the influence of the Sn mole fraction on the device MIR spectral photoresponse and switching characteristics is investigated. It is found that the use of 15% of Sn containing can allow achieving the highest responsivity at 2 µm optical window, while maintaining a low dark noise effects. The optimized device is the implemented in an optical inverter gate in order to study the device switching characteristics. The obtained results demonstrate the capability of the proposed PT structure for promoting enhanced optical gain with high switching capabilities. Therefore, these findings open the perspective for the design of alternative MIR sensors, offering improved photoresponse and low noise, which are highly suitable for newly emerging CMOS-compatible optical communication and optoelectronic applications.