Light emission properties of amorphous silicon quantum dots

We theoretically study the light emission properties of amorphous silicon quantum dots (a-Si QDs). From an analysis of the radiative tunneling rate, we first assert that the dominant recombination process of a-Si QDs smaller than 2.4 nm in diameter is a direct band-to-band recombination. Our tight-binding calculations for direct band-to-band recombination reproduce the peak energies of experimental photoluminescence (PL) due to Park et al. This fact indicates that the PL origin is mainly the direct band-to-band recombination, which in other words indicates that the blueshift of the PL peak energy is attributed to quantum confinement rather than to the so-called spatial confinement effect related to radiative tunneling.