Observation of strong Si/Si1−xGex narrow quantum-well near-edge luminescence under applied hydrostatic pressure

Abstract

We report the first measurements of band-gap energy versus applied hydrostatic pressure in the Si1−xGex system, a result achievable only with the recent availability of high-quality alloys. The Si/Si1−xGex (x=0.05–0.25) quantum wells used here were prepared by molecular beam epitaxy, and produced relatively intense photoluminescence (PL). Indeed, this PL emission from just two 25-Å-thick quantum wells was found to be comparable to that from high-optical quality, ultrahigh-purity bulk Si. A clear no-phonon emission line is found in the low-temperature (6 K) PL which displays a strictly linear PL energy dependence with pressure. The alloy and Si pressure dependencies (−1.50 and −1.52 meV/kbar) were found to be virtually identical thus proving the luminescence is from a ‘‘shallow’’ electronic state and associated with the X band gap of the pseudomorphically strained alloy.