Ge Doping of PtSe₂ for Bandgap Opening via GeSe Dynamic Diffusion Barrier Enabling High Sensitivity SOI-Based SWIR...

An innovative GeSe dynamic conversion diffusion barrier-assisted in situ selenization strategy is proposed on Si/SOI bonded substrates, realizing in situ Ge doping of PtSe₂, suppressing Pt-Si interdiffusion, and fabricating high-quality PtSe₂/Si/SOI heterojunctions. Density functional theory reveals that Ge doping widens the PtSe₂ bandgap, converting it from a semimetal to a semiconductor. Finite-difference time-domain analysis demonstrates that the Si/SOI architecture boosts depletion-region light absorption efficiency. The PtSe₂/i‑Si/n⁺‑SOI PIN photodetector exhibits self-powered broadband response from 532 to 2200 nm, extending Si-based photodetection into the short-wave infrared (SWIR). It demonstrates a high rectification ratio of 10⁷, low surface and bulk leakage currents of 2.7 × 10^-9 A cm^-1 and 2.6 × 10^-6 A cm^-2, rapid dynamics with rise/fall times of 6.6/10.4 µs, and a 3 dB cutoff frequency of 123 kHz. At 1310 nm, the responsivity and specific detectivity reach 85.21 µA W^-1 and 6.39 × 10⁶ Jones. The device also shows promising coded communication capability at 1550 nm. This work resolves the critical Pt-Si interdiffusion issue, providing a new pathway for Si-compatible SWIR photodetection and optical communication integration. Looking ahead, replacing the intrinsic layer in the PIN architecture with Ge is expected to further enhance the device's photoresponse performance in the SWIR.