Broadband Photo- and Electroluminescence from Bulk Silicon via Strong Photonic Confinement

Abstract

Silicon indirect bandgap fundamentally limits its ability to emit light, hindering the development of silicon-based light sources. Here, we explore a conceptually new solution to this long-standing challenge. We demonstrate ultrabroadband photo- and electroluminescence from bulk silicon, enabled by a radiative pathway mediated by momentum-expanded photonic states that bypass phonon-assisted transitions. This mechanism, previously demonstrated using metallic nanoparticles as photon confiners, is here realized in an all-silicon system using embedded sub-1.5 nm silicon nanoparticles. Since such ultrasmall particles possess negligible intrinsic emission efficiency, we instead demonstrate that they act as photonic confiners, enabling radiative recombination in the surrounding bulk material. The agreement with prior metal-based systems confirms that confinement size, rather than material composition, governs the activation of radiative transitions in a momentum-forbidden system. The emission spans the visible to near-infrared spectral range, with electroluminescence in an undoped semiconductor device visible under ambient conditions and a quantum efficiency estimated as ~0.2%. These findings establish a new route to efficient light emission in silicon and reveal a hybrid light-matter regime in which extreme photonic confinement reshapes the electronic transition landscape.