Theoretical study of light-emission properties of amorphous silicon quantum dots

In order to clarify the mechanism of the photoluminescence (PL) from amorphous silicon quantum dots (a-Si QDs), we calculate, in the tight-binding scheme, the emission spectra and the radiative recombination rate P of the direct band-to-band recombination process. For a-Si QDs smaller than 2.4 nm in diameter, our calculations beautifully reproduce the peak energy E-PL of the experimental PL peak [N.-M. Park et al., Phys. Rev. Lett. 86, 1355 (2001)]. Our analysis also show that (i) the emission energy can be tuned into the visible range of light from red to blue by controlling the sizes of a-Si QDs, and that (ii) P calculated for a-Si QDs is higher by two to three orders of magnitude than that for crystalline Si QDs. From these results, we assert that a-Si QDs are promising candidates for visible, tunable, and high-performance light-emitting devices.