Saturation Spectroscopy of Impurity transitions in GaAs/AlGaAs MQWs
Abstract
We have performed a series of magneto-transmission and magneto-photoconductivity measurements on two donor-doped GaAs/Al_0.3Ga_0.7As multiple-quantum-well samples (well width 20nm) as a function of power density with the UCSB Free Electron Laser (FEL) over a wide range of laser power under steady state conditions in fields up to 8T. Sample 1 was doped in the GaAs well centers only at 2 × 10^10cm-2, while sample 2 was doped in both the well and barrier centers (2 × 10^10/4 × 10^10cm-2). Saturation of the D^0(1s-2p^+) transition, the D^--singlet transition and CR was observed. From analysis of the D^0(1s-2p^+) data in sample 1 effective lifetimes were found to vary systematically with laser frequency, decreasing from 62ns at 84cm-1 (2p^+ state below the lowest Landau level) to 3ns at 124cm-1 (2p^+ state above the lowest Landau level). Saturation of the D^--singlet transition was observed in sample 2. The absorption coefficient initially increased by up to 40% and then showed complet quenching at higher laser powers, very different from the neutral donor results. * Supported in part by the ONR/MFEL Program.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 1996
- Bibcode:
- 1996APS..MAR.H3326M