  We propose a novel concept of achieving silicon quantum dots with radiative
rates enhanced by more than two orders of magnitude up to the values
characteristic for direct band gap semiconductors. Our tight-binding
simulations show how the surface engineering can dramatically change the
density of confined electrons in real- and $k$-space and give rise to the new
conduction band levels in $\Gamma$-valley, thus promoting the direct radiative
transitions. The effect may be realized by covering the silicon dots with
covalently bonded electronegative ligands, such as alkyl or teflon chains
and/or by embedding in highly electronegative medium.
