Time-resolved screening of the piezoelectric field in InGaAs/GaAs V-shapedquantum wires of variable profile

InGaAs/GaAs V-shaped quantum wires grown in grooves with either(lll) or (41 1) sidewalls have been studied by ps-transient photoluminescence as a funct ion of the excitation intensity. The optical nonlinearity associated with t he screening of the internal piezoelectric field is temporally monitored by the blue shift of the spectrally resolved photoluminescence, occurring in the first 150 ps after the laser pulse, followed by a red shift at longer d elays, Such an energy shift strongly depends on the photoexcited carrier de nsity and reaches a maximum value of about 14 meV in the (411) wires, Despi te their larger piezoelectric field, we observe a smaller energy shift in w ires with (111) sidewalls, due to the enhanced confinement which localizes the wire wavefunction at the bottom of the groove. The observed energy shif ts are consistent with the theoretical calculation of the polarization char ge density induced by the strain via the piezoelectric effect. (C) 1999 Aca demic Press.