A. B. Dzyubenko

Trions in ZnSe‐Based Quantum Wells Probed by 50 T Magnetic Fields

Singlet and triplet states of negatively charged excitons (trions) in ZnSe/(Zn,Be,Mg)Se quantum wells have been studied by means of photoluminescence in pulsed magnetic fields up to 50 T. Singlet state binding energies, measured for different well widths ranging from 48 to 190 A, show a monotonic increase with growing magnetic fields with a tendency to saturation. This behavior is in qualitative agreement with results of model calculations. Quantitatively, the binding energy of singlet states is underestimated by about 50%. The triplet state assigned to the dark triplet becomes detectable in magnetic fields above 15 T. A crossover of the triplet and singlet states is expected in magnetic fields of about 50 T.

Free versus donor‐bound charged excitons in quantum wells: Spectra of states and optical transitions in magnetic fields

We theoretically consider binding of quasi‐2D charged excitons X− on isolated donor ions D+ located at various distances from the quantum well. We establish how many different singlet Xs− and triplet Xt− bound states a donor ion D+ can support in magnetic fields B > 5 T. We show that dark X− states acquire finite oscillator strengths and that shake‐up transitions become allowed in photoluminescence in the presence of the D+ ion.

INTERNAL TRANSITIONS OF NEUTRAL AND NEGATIVELY CHARGED MAGNETOEXCITONS IN GaAs NANOSTRUCTURES : THE IMPORTANCE OF SYMMETRY

Cyclotron Resonance (CR) of free electrons and holes and internal transitions of their bound complexes have been studied in GaAs/AlGaAs quantum wells in high magnetic fields by Optically Detected Resonance (ODR) spectroscopy. Two nearly degenerate 1s→2p+ internal exciton transitions (IETs), as well as two well-separated 1s→2p- IETs resulting from the two distinct heavy-hole magneto-excitons were observed. Measurements of both electron and hole CR and these IETs in the same sample evidence the predicted consequences of the symmetry of the magneto-exciton Hamiltonian. Extensions of these studies to samples that showed neutral (heavy-hole hhX) as well as negatively charged (X-) exciton photoluminescence-lines have permitted the first observation of internal transitions of X-. Both singlet and triplet transitions of X- were observed, and new physics associated with translational invariance for this interesting three-particle complex was revealed. The observation of electron and hole CR and several IETs in a single sample exemplifies the promise of the ODR technique for the study of semiconductor nanostructures.