Charge Transfer Luminescence in (gain)as/gaas/ga(nas) Double Quantum Wells

Charge transfer excitons are studied in double quantum well structures consisting of a (GaIn)As and a Ga(NAs) layer separated by a GaAs film of variable thickness. With decreasing barrier thickness, the gradual change from a spatially direct exciton within the (GaIn)As well to a charge transfer exciton bound across the GaAs spacing layer is observed. The optical spectra are well reproduced by a fully microscopic theory and band structure calculations based on the k·p method using a weak type-I valence band offset of approximately (45±40)meV at the Ga(NAs)/GaAs interface.