Study of Single-Photon Detection Using a Back-Gated Si Single-Electron Transistor

Ultra-sensitive single-photon detection is important for applications like spectroscopy and quantum sensing. Although Si detectors are CMOS-compatible, their low absorption limits their sensitivity. We developed a top-gate-free single-electron tunnelling transistor (SET) using a codoped thin-Si film in a silicon-on-insulator (SOI) structure, achieving high-sensitivity detection at 1780 nm. The mechanism includes SET current shifts and random telegraph signals (RTS), with noise equivalent power (NEP) estimated at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$5.89 \times 10^{-19} \mathbf{W}\ \mathbf{Hz}^{-1 / 2}$</tex>. Comparison with aluminium top-gated devices shows a trade-off between electrostatic control and photon absorption. These results illustrate a promising all-silicon strategy for future long-wavelength photon sensing.