Phototransport spectroscopy of ensembles of Si quantum dots

Abstract

We studied the photocurrent spectra (PCS) in ensembles of Si nanocrystals (NCs) embedded in a SiO2 matrix as a function of the average NC size and temperature, above the conductivity percolation threshold of the ensembles. The PCS clearly manifest the quantum confinement effect in this high NC density regime, where the photoluminescence is already quenched due to carriers' delocalization. The PCS are also shown to provide information on the recombination mechanism by utilizing the light soaking effect observed in our samples, indicating that the oxide encapsulation efficiently passivates the dangling bonds on the surface of the NCs. These results are consistent with our previous conclusions regarding the radiative emission and the extended-states' transport mechanisms in ensembles of Si NCs. In turn, the latter conclusion provides insight into the significance of surface recombination even in systems where the optical absorption depth is much larger than the size of the light absorbing particles.