Two-color picosecond and continuous-wave experiments on anti-Stokes and Stokes carrier-transfer phenomena in GaAslAl(x)Ga(1-x)As and InGaP2/AlxGa1-xAs heterostructures

We present direct evidence of the two-step absorption process in anti-Stoke s photoluminescence in both GaAs/AlxGa1-xAs and InGaP2/AlxGa1-xAs heterostr uctures using two-color picosecond and continuous-wave photoluminescence ex periments. We show information about the lifetime of the defect states that participate in the two-step absorption process. As a result, we conclude t hat the long-lived states rather than excitons play the dominant role in th e two-step absorption process. We also study the possible contribution of t he two-step absorption process to Stokes carrier transfer in GaAs/AlxGa1-xA s asymmetric double quantum well structures.