Free electron laser saturation spectroscopy of neutral donors and negative donor ions confined in GaAs/AlGaAs quantum wells

Abstract Saturation of the D 0 1s-2p^ + transition, the D − -singlet transition and CR has been studied in donor (Si)-doped GaAs/AlGaAs multiple-quantum-well samples by magneto-transmission and magneto-photoconductivity measurements with the UCSB free electron laser. Effective lifetimes of the D 0 1s-2p + transition were found to vary systematically with laser frequency, decreasing from 62 ns at 84≈cm −1 to 3 ns at 124 cm −1 . The absorption coefficient of the D – -singlet transition initially increased by up to 40% and showed complete quenching at higher laser powers.