Interfacial Strain Fields for Nano-Carrier-Confinement and Efficient Bandgap Emission in Silicon Under 980-nm Laser Excitation

Ordinary Czochralski silicon (CZ-Si) is known to be inferior in radiative recombination at the bandgap. Interfacing CZ-Si with sol-gel based silica coatings improves the bandgap emission significantly by introducing random strain fields; such results have been reported in several publications and presentations in the literature. In all previous work, the emission band can be modeled by a combination of uncorrelated electron-hole and phonon three particle process. In this work, we report an enhancement in carrier recombination from p-Si photoluminescence that is unorthodoxly dominated by excitonic carrier recombination. The nano-region carrier-confinement results in photons of energy <i>h</i>n with intensity of spectral form e^1/2associated with correlated carrier recombination, where e = <i>h</i>n - <i>E</i>_B + <i><u>E</u></i>_exc + <i>E</i>_TO, <i>E</i>_B is the band gap, <i>E</i>_exc is the exciton binding energy, and <i>E</i>_TO is the transverse optical phonon energy.