Ultra-high performance Si0.5Ge0.5 source Hetero-Dielectric TFET photosensor for near-infrared (NIR) detection

This work investigates the optical performance of a ${\mathrm{Si}}_{0.5}{\mathrm{Ge}}_{0.5}$ source Hetero-Dielectric (HD) TFET photosensor for detection of light in the near-infrared (NIR) region 750 to 1050 nm. The ${\mathrm{Si}}_{0.5}{\mathrm{Ge}}_{0.5}$ source HD-TFET photosensor incorporates a heterogate configuration with stacked dielectric layers ${\mathrm{HfO}}_2/{\mathrm{SiO}}_2$ beneath a silicon photosensing gate $n^{+}$ and employs a $p^{+}$ ${\mathrm{Si}}_{0.5}{\mathrm{Ge}}_{0.5}$ source, a $n^{+}$ silicon drain to improve carrier tunneling. The optical response is analyzed under both illuminated and dark conditions by evaluating key physical parameters, including energy band alignment, optical generation rate, band-to-band tunneling (BTBT) rate, and electron density distribution. Sensitivity, Spectral sensitivity ($S_n$), signal-to-noise ratio (SNR), responsivity ($R$), external quantum efficiency ($\eta$), and detectivity (D), are evaluated based on incident light wavelength ($\lambda$) and gate voltage ($V_{gs}$). Simulation results demonstrate that the ${\mathrm{Si}}_{0.5}{\mathrm{Ge}}_{0.5}$ source HD-TFET photosensor achieves superior optical performance, particularly under low-light and NIR conditions, compared to conventional Si-based and Ge-source TFET photosensors. This is attributed to the enhanced BTBT rate and efficient transport of photogenerated carriers enabled by the heterogate structure. Performance metrics are compiled and compared, highlighting the effectiveness of the ${\mathrm{Si}}_{0.5}{\mathrm{Ge}}_{0.5}$ source HD-TFET photosensor in delivering high spectral sensitivity of 55.35, responsivity of $1.6\times 10^5$ A/W, external quantum efficiency of $1.76\times 10^5$, and enhanced sensitivity, indicating that it is a promising technology for low-power photodetection applications.