Quantum confinement and hybrid integration in silicon light emitters toward scalable on-chip photonics.

Silicon photonics provides a scalable platform for photonic integrated circuits (PICs) through compatibility with mature complementary metal-oxide-semiconductor (CMOS) processing. However, silicon's indirect bandgap intrinsically limits radiative recombination efficiency, necessitating material and structural strategies to enhance light emission. This review critically evaluates recent progress in silicon based light-emitting devices enabled by quantum confinement and hybrid integration approaches. Low-dimensional architectures including quantum wells (2D), nanowires (1D), and quantum dots (0D) are analysed in terms of emission control, threshold behaviour, thermal stability, and integration maturity. Advances in heterogeneous III-V/Si integration, GeSn group-IV heterostructures, nano-ridge epitaxy, and cavity-enhanced photonic crystal platforms are discussed from a materials and manufacturability perspective. Collectively, these developments reflect a progressive transition from passive silicon photonics toward reproducible, scalable light-generating platforms suitable for coherent and spectrally controlled optical systems.