Confinement-Enhanced Core–Shell Avalanche Photodetectors

Silicon-based avalanche photodetectors (Si-APDs) are promising candidates for complementary metal oxide semiconductor (CMOS)-compatible optoelectronic systems, leveraging their inherent multiplication mechanism to compensate for silicon’s weak absorption at the near-infrared (NIR) range through advanced structural engineering. However, conventional free-space Si-APDs suffer from inevitable limitations, most notably spatially nonuniform avalanche triggering arising from stochastic carrier injection, excessive multiplication noise caused by unregulated avalanche paths, and surface recombination losses at heterojunction interfaces, which collectively constrain their development in emerging NIR detection. Herein, we construct and demonstrate a novel SiO2-passivated Si nanowire (SiO2-SiNW)/graphene confinement-enhanced photodetector, where vertical SiO2-SiNWs function as a core–shell nanoresonator system. The proposed design structure leverages photon confinement to enhance light absorption at 1550 nm, while the localized field enhancement at the SiNW/graphene vertical van der Waals (vdW) interface facilitates avalanche photodetection. Through advanced structural engineering, the device exhibits a responsivity of 56.58 A/W and a high avalanche gain of 2.64 × 104, attributed to the synergistic interplay of nanoresonator-enhanced light–matter interaction and efficient carrier multiplication within the confined avalanche regime. The strategic integration of dielectric-engineered nanostructures with vdW heterostructures establishes a versatile platform for developing optoelectronic systems operating at NIR telecommunications, while enabling precise control over carrier transport and photon management at the nanoscale.