How to convert group-IV semiconductors into light emitters

In this paper, we review current theoretical attempts to optimize the radiative inter-band transition rates in Si and Ge. Large optical emission rates in the far infrared have recently been predicted in laterally strained Ge and Ge-based superlattices. In strained bulk Si, however, a nearly 12% hydrostatic expansion would be needed to achieve the same goal. Si-dominated strained layer superlattices or quantum wires with various chemical modifications do not seem to be suitable to yield optical inter-band transition rates comparable to GaAs. Up to now, the only exception which has been predicted is siloxene.