Enhanced optical performance of a dual-drain vertical TFET photosensor for near-infrared light detection

This paper details the optical performance of a dual-drain vertical TFET (DDV-TFET) based photosensor designed for light detection in the near-infrared (NIR) region (0.7–1.0 μm), employing silicon with N⁺ doping as the photosensing gate. The optical performance of DDV-TFET photosensor is assessed by observing the variations in energy band diagram, optical voltage and band-to-band tunnelling rate of the charge carriers under both Light and dark conditions. The incorporation of N⁺ pockets and back gate facilitates an increased tunneling rate of charge carriers at the source-channel interface, thereby enhancing the modulation of the channel behavior when light is absorbed inside the photosensing gate. The presented DDV-TFET photosensor demonstrates enhanced optical performance when detecting light at low illumination intensity of 0.5 W/cm² incident on the photosensing gate. TCAD-based simulation results reveal that silicon photosensing gate with an optimal thickness of 20 nm and a pocket doping concentration of 1 × 10¹⁹ cm⁻³ achieves a sensitivity of 3.59 × 10⁵, a responsivity of 14.8 A/W, a detectivity of 5 × 10¹¹ Jones and a signal-to-noise ratio (SNR) of 111 dB when detecting incident light in the NIR range. Furthermore, the optical performance of DDV-TFET based photosensor is observed for different $k$-value of gate oxide and germanium as source material, which reveals that low-k gate oxide offers higher sensitivity and SNR. Conversely, utilizing low band gap source material causes degradation in the sensitivity and SNR of the investigated photosensor.