Luminescence from monolayer-thick Ge quantum wells embedded in Si

Abstract
We report on the observation of strong electroluminescence and photoluminescence from a Si/Ge quantum structure involving a two-monolayer-thick Ge layer in a bulk Si matrix. It has been proposed that when a conduction-band electron is scattered at the Si-Ge interface, the normally forbidden no-phonon (NP) interband transition is allowed due to mixing of different bulk momenta. The luminescence spectra of our samples consist of a NP line and a transverse-optical (TO) phonon replica originating from the Ge layers. The TO-phonon energy coincides with a Si-Ge mode, confirming the importance of the interface.