Spin-polarized excitons in pseudomorphic, strained In0.16Ga0.84As/Al0. 29Ga0.71As quantum wells on a GaAs substrate

Circularly polarized excitation light from a tunable Ti-doped sapphire laser has been used to produce spin-polarized excitons in strained, pseudomorphic In0.16Ga0.84As/Al0.29Ga0.71As quantum wells (QWs) grown on GaAs substrates. By analyzing the degree of circular polarization of the exciton luminescence and by studying the depolarization effect of a transverse magnetic field, the optical lifetime and the spin-relaxation time of excited carriers can be determined in relatively wide wells. We further show that circular excitation offers a relatively simple means to discriminate unambiguously between light- and heavy-hole excitons. We have thus made measurements that yield optically determined band offsets for the QW system under investigation.