Temperature dependence and recombination behavior of trapped charge carriers in ZnCdSe/ZnSe multiple quantum wells are investigated employing surface acoustic waves. These weakly perturb the carrier system, but remain highly sensitive even at small c
onductivities. Using this non-invasive probe we are able to detect persistent photoconductivity minutes after optical excitation. Measurement of exciting photon energies, the temperature dependence and ability to quench the conductivity with energies lower than the bandgap, support the notion of spatial separation of electrons and holes in the wells, due to random local potential fluctuations possibly induced by compositional fluctuations.
We demonstrate a method to grow height controlled, dislocation-free InGaAs quantum posts (QPs) on GaAs by molecular beam epitaxy (MBE) which is confirmed by structural investigations. The optical properties are compared to realistic 8-band k.p calcul
ations of the electronic structure which fully account for strain and the structural properties of the QP. Using QPs embedded in n-i-p junctions we find wide range tunability of the interband spectrum and giant static dipole moments.
