Performance engineering of eco-friendly Mg2Si/Si photodetectors: TCAD-validated advantages of PIN over PN structures for visible-NIR detection

The Mg2Si/Si heterojunction PN and PIN structure models have been established by the Atlas module of Silvaco TCAD software, and the detection properties of PN and PIN photodetectors (PDs), such as energy band, current–voltage, responsivity, external quantum efficiency (EQE), noise equivalent power (NEP), detectivity (D*), on/off ratio, and response and recovery times, have been studied. Cumulative results based on different structures of those Mg2Si/Si heterojunction PDs showed that responsivity (0.45 A/W), EQE (60.86%), NEP (1.45 × 10−12 W Hz−1/2), D* (7.42 × 1011 Jones), and on/off ratio (7452), response time (8.56 × 10−10 s), and recovery time (5.27 × 10−10 s) of PIN structure has been enhanced compared to those of PN structure by 10%, 18%, 82%, 213%, 318%, 56.33%, and 6.39%, respectively. The intrinsic layer (i-layer) in the PIN architecture extends the depletion width, enhancing long-wavelength infrared (LWIR) absorption through increased photon interaction volume, thereby significantly improving responsivity and EQE. The low dark current characteristic of the PIN architecture enhances detector performance by improving NEP and D*. Furthermore, its extended detection properties and strong built-in electric field enhance the on/off ratio. The PN and PIN heterojunction PDs can detect the visible and near-infrared wavelengths in the range of 400–1500 nm. The simulation results can be used to guide the fabrication of environmentally friendly Mg2Si/Si heterojunction PDs.