Internal transitions of charged magneto-excitons in II-VI quantum well heterostructures
Abstract
Recently, optically detected resonance (ODR) spectroscopy has been used to investigate electronic states of free charge carriers and their complexes, as well as bound states of neutral and charged donors. It combines far-infrared and near-infrared methods by measuring small (0.1%-10%) intensity changes of particular photoluminescence features induced by resonant absorption of FIR radiation. We report ODR experiments on II-VI quantum well (QW) heterostructures. We have observed electron cyclotron resonance (e-CR), and what we believe to be internal triplet transitions of X^- for two 80ÅCdTe/Cd_0.7Mg_0.3Te QW's. Sample 1 is modulation doped (ne = 3.6 × 10^11 cm-2). The electron density of sample 2 can be tuned via optical pumping above a 1000Åthick superlattice (SL) (30ÅÅminiband, separated by a 200Åbarrier from the well. In low fields, for filling factors ν > 2, we observe a broad but symmetric e-CR. In contrast, for filling factor ν < 2 we observe a strong asymmetry of the CR feature on the low field side, very similar to previous experiments in GaAs/AlGaAs QW structures. By analogy we attribute the low-field asymmetry to a band of ionizing triplet-like transitions of X^-. Work supported in part by NSF DMR 9722625 and DFG OS98/6.
- Publication:
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APS March Meeting Abstracts
- Pub Date:
- March 2001
- Bibcode:
- 2001APS..MARG30005M