Optically gated SiGe point-tunneling TFET with V _OP -assisted transport for ultra-sensitive near-infrared photodetection

Abstract An optically gated vertical SiGe point-tunneling tunnel field-effect transistor is proposed and systematically investigated for low-power near-infrared (NIR) photodetection applications. The device exploits a silicon optical gate combined with a Si 0.7 Ge 0.3 source to enhance optical absorption and strengthen electrostatic control at the tunneling junction. Under NIR illumination, photogenerated carriers in the optical gate induce an additional gate potential, which significantly narrows the tunneling barrier and amplifies band-to-band tunneling through a V OP -assisted point-tunneling mechanism. Comprehensive TCAD simulations demonstrate pronounced wavelength-dependent photoresponse in the 750–1050 nm range, with a peak sensitivity of approximately 8.9 × 10⁴ at V GS = 0.1 V and a maximum signal-to-noise ratio of ∼100 dB at 750 nm. The proposed device achieves a responsivity of up to 4.0 × 10 3 A W −1 and an external quantum efficiency of ∼2.0 × 10 3 , indicating strong internal gain enabled by tunneling-dominated transport. Optical power, temperature, and source mole-fraction analyses confirm robust and stable operation, with Si 0.7 Ge 0.3 identified as the optimal source composition due to its balanced trade-off between enhanced tunneling and suppressed dark current. Benchmarking against recently reported TFET-based photodetectors highlights the superior sensitivity, signal integrity, and NIR detection capability of the proposed architecture, making it a promising candidate for ultra-low-power optical sensing applications.