High Photosensitivity in Band-to-Band Tunneling Regime of Carbon Nanotube Field-Effect Phototransistor: Numerical Investigation

In this paper, we show how the band-to-band tunneling (BTBT) regime of ultra-scaled carbon nanotube fieldeffect transistor (CNTFET) can be exploited to get ultra-high photosensitivity to low infrared (IR) optical power. The CNT-based phototransistor has been computationally assessed by solving self-consistently the Poisson solver including the photovoltage with the non-equilibrium Green’s function (NEGF) formalism in the ballistic limit. This quantum simulation approach is adopted to take into account the BTBT mechanisms on which the photosensing principle is based in the proposed nanodevice. The light-induced gate photovoltage is adopted as photosensing principle. It has been found that the BTBT CNTFET can exhibit subthermionic optical swing. In addition, high photosensitivity can be recorded in BTBT regime to low gate photovoltages induced by weak IR incident optical powers. The obtained results indicate that the proposed nanoscale CNT phototransistor operating in BTBT photosensing regime can serve the modern optoelectronics, which is in dire need for ultra-sensitive phototransistors with low detection limits.