P-N Nanoporous Silicon Fabrication Using Photoelectrochemical Etching and Ultrasonic Vibration and Liquid-Phase Bonding for Optoelectronic Applications.

We systematically investigated the optical properties of P-N nanoporous silicon (NPS) diodes fabricated using photoelectrochemical etching and ultrasonic vibration (PEEU), followed by liquid-phase bonding and thermal treatment. Ultrasonic vibration during etching promoted uniform pore formation by enhancing reactant diffusion and suppressing hydrogen bubble accumulation, while laser-induced photocarriers improved etching selectivity, facilitating the formation of NPS with pronounced quantum confinement. The fabricated NPS devices exhibited significantly enhanced photoluminescence (PL) and electroluminescence (EL) properties, with an average external quantum efficiency of 7.3% at a bias of 10 V. Subsequent liquid-phase bonding and thermal annealing further enhanced structural stability and interface quality, resulting in an 180% increase in PL intensity. These results demonstrate that the combination of PEEU with liquid-phase bonding and thermal annealing yields a versatile approach to tailor the optical and electrical properties of P-N porous silicon nanostructures for high-performance light-emitting diodes and quantum-confined silicon photonics, highlighting the critical role of process-induced nanostructures and thermal modifications in device performance.