Enhanced infrared photoresponse of a new InGaZnO TFT based on Ge capping layer and high-k dielectric material

Abstract In this paper, a novel InGaZnO (IGZO) Infrared (IR) thin-film Phototransistor (Photo-TFT) consisting of Germanium capping layer (Ge-CL) and high-k dielectric material is proposed and numerically investigated. The role of introducing Ge-CL/IGZO heterojunction and high-k dielectric such as HfO2, ZrO2, Ta2O5 and TiO2 in achieving the dual benefit of IR photodetection ability and reduced dark noise effects is demonstrated. It is found that the proposed Ge-CL/IGZO Photo-TFT with appropriate gate oxide material can offer high detectivity of 2.3 × 1014 Jones, superior current ratio exceeding 200 dB and high IR responsivity of 4.1 × 102 A/W. These enhancements are attributed to a mixture of two effects; firstly, the introduction of p-type Ge-CL leads to form a p-n junction with IGZO, thus enhancing the separation and transfer mechanisms of photo-induced electron/hole pairs. Secondly, the use of high-k dielectric materials enables better control of the channel conductivity, allowing reduced power consumption. Therefore, we believe that the use of Ge-CL with suitable high-k dielectric material pinpoints a new pathway to design high IR photoresponse sensors based on cost-effective IGZO TFT building block, which makes it potential alternative for high-performance optoelectronic systems.