Performance analysis of highly sensitive vertical tunnel FET for detecting light in near-IR range

In this paper, an optically gated vertical tunnel field-effect transistor (OG-VTFET) based photodetector with different gate oxides is investigated to detect incident light with narrow-separated wavelengths (~ 100 nm) in the near-infrared (NIR) range (750–1050 nm). The optical performance parameters such as spectral sensitivity (S_n), signal-to-noise ratio (SNR), quantum efficiency (ƞ), and responsivity (R) are observed to improve in the NIR range due to improvement in the ON-current (I_ON), subthreshold swing (SS_avg), and dark current (I_Dark) offered by OG-VTFET. OG-VTFET with HfO₂ as gate oxide shows enhancement in the dual-line tunneling of charge carriers around the source-channel (S–C) interface, which eventually leads to improvement in I_ON and SS_avg compared to SiO₂ at wavelengths (λ) of light ranging from 750 to 1050 nm. Therefore, a high S_n of ~200 is achieved for the proposed photodetector under the light condition when HfO₂ is used as a gate oxide. However, reduction in the dark current (I_dark) using a low- \(K\) $K$ dielectric i.e. SiO₂ as gate oxide reports a higher SNR value of ~82.2 dB compared to HfO₂ which offers ~60 dB of SNR at λ of 750 nm. Moreover, a portion of the channel is elevated around the gate corner to mitigate the corner effects at the S–C interface, which leads to an increase in the light-to-dark current ratio (I_light/I_dark) for the proposed photodetector when λ varies from 1050 to 750 nm. In addition, a heavily doped pocket deposited around the source region provides a better electric field at the S–C interface after an optical voltage is developed across the photosensing gate for the incident light falling on it. The quantum efficiency (ƞ) and responsivity (R) of OG-VTFET-based photodetector with HfO₂ gate oxide are eventually improved as more electron–hole pairs (EHPs) are generated under the illuminated state even at high λ of 1050 nm. ƞ and R are reported to be 2.1 and 1.77 A/W, respectively for OG-VTFET-based photodetector at λ of 1050 nm. Finally, the reliability concern of the proposed photodetector is examined by incorporating interface-trap charges (ITCs) at the oxide–semiconductor (O–S) interface, and an insignificant change in the SNR value is observed when SiO₂ is used as the gate oxide.