Observation of many-body effects and band-gap renormalization in low-dimensional systems with built-in piezoelectric fields

We show that many-body effects and band-gap renormalization can be easily produced in strained-layer quantum wells with internal built-in piezoelectric fields, under photoexcitation. Our observation was made at low temperature by comparing the behavior of ${\mathrm{Ga}}_{0.92}$${\mathrm{In}}_{0.08}$As-GaAs strained-layer quantum wells grown along the (111) and (001) directions and tuning the densities of photoinjected carriers over several decades. Comparison between experimental data and the results of Hartree calculations including the charge space effects reveals that many-body interactions are photoinduced.