Influence of band alignment on recombination in pseudomorphic Si1−xGex∕Si quantum wells

Unique potential lineup of pseudomorphic Si1−xGex∕Si quantum wells (QWs) allows negative charge buildup in the near-surface region. Significant local charge imbalance created thereby between electrons and holes diminishes the efficiency of the otherwise dominating, nonradiative Shockley-Read-Hall recombination in the QWs at a low level of photoexcitation, which is evidenced by anomalous evolution of photoluminescence intensity and internal quantum efficiency with increasing excitation density.