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.