Near-infrared optical sensor based on band-to-band tunnel FET

Abstract

In this work, three different device structures based on the band-to-band tunnel field effect transistor (TFET) have been proposed for near-infrared optical sensing application. Comparison has been made on their spectral response to different wavelengths (0.7–1 µm). The device with Ge n+ pocket at the source-channel junction outperforms the other two with a better ON current ION (63.4 μA) and steeper subthreshold swing SS (28 mV/dec). Further optimization of this device is done showing influence of source doping and high-k dielectric material on its transfer characteristics. It is found that the threshold voltage VT and ION are sensitive to wavelength variations. VT increases by ~ 10–20 mV and ION decreases by 35% in the considered wavelength range at a gate doping of 1 × 1018/cm3. The sensitivity of these proposed devices are determined relative to the change in current corresponding to the change in illumination wavelength. With the utilization of Ge n+ pocket, high-k gate dielectric the peak spectral sensitivity increases to 10.53 at the illumination intensity of 0.5 W/cm2 and also it can determine firmly separated spectral lines (100 nm) in the near infrared range because of its steep sub-threshold swing.