The unique type-II potential lineup of pseudomorphic Si1-xGex/Si quantum wells (QWs) allows a negative charge buildup in the near-surface region. As a result, diminished Shockley-Read-Hall (SRH) recombination is observed in the surface-side QW in a double QW geometry where charge imbalance due to the negative charge buildup plays a critical role. Spectral changes due to the charge redistribution under longitudinal electric fields indicate that the second QW on the substrate-side is key to the charge imbalance, and allows an enhanced internal quantum efficiency of radiative recombination in the surface-side QW. (c) 2005 Published by Elsevier B.V.