Dmitry R. Yakovlev’s research while affiliated with TU Dortmund University and other places

Optical properties of (Zn,Mn)Se/(Zn,Be)Se quantum wells containing a two-dimensional electron gas with densities varying from 109 to 5.5 × 1011 cm-2 have been studied in magnetic fields up to 45 T. A strong s — d exchange interaction of free electrons with magnetic Mn ions results in a giant Zeeman splitting of conduction band states, that has been exploited for manipulation with a spin polarization of the electron gas. Critical behavior of the photoluminescence and reflectivity linewidths and of the energy shift of the lines in magnetic fields in vicinity of integer filling factors 2 and 1 has been found and analyzed. Key wordsquantum well–diluted magnetic semiconductor–excitons–trions

Optical properties of a two-dimensional electron gas in ZnSe/(Zn,Be,Mg)Se quantum well structures have been examined by means Optical properties of a two-dimensional electron gas in ZnSe/(Zn,Be,Mg)Se quantum well structures have been examined by means of photoluminescence and reflectivity techniques in external magnetic fields up to 50 T. For the studied structures, the Fermi of photoluminescence and reflectivity techniques in external magnetic fields up to 50 T. For the studied structures, the Fermi energy of the two-dimensional electron gas falls in the range between the trion binding energy and the exciton binding energy, energy of the two-dimensional electron gas falls in the range between the trion binding energy and the exciton binding energy, which keeps the dominating role of Coulombic interactions between electrons and photoexcited holes. Characteristic peculiarities which keeps the dominating role of Coulombic interactions between electrons and photoexcited holes. Characteristic peculiarities of the optical spectra are discussed. of the optical spectra are discussed.

In modulation-doped quantum well structures with electron concentration of about 10(11) cm(-2), a new resonant optical transition involving four particles (one hole and three electrons) was found in external magnetic fields in photoluminescence excitation and reflectivity spectra. This transition reveals as a narrow line between exciton and trion lines. It is identified with a combined process in which a photocreated exciton binds with an electron forming a trion and promotes for the second electron a transition to higher Landau levels.

Excitons and charged excitons (trions) are investigated in ZnSe-based quantum well structures with (Zn,Be,Mg)Se and (Zn,Mg)(S,Se) barriers by means of magneto-optical spectroscopy. Binding energies of negatively (X−) and positively (X+) charged excitons are measured as functions of quantum well width, free carrier density and in external magnetic fields up to 47 T. The binding energy of X− shows a strong increase from 1.4 to 8.9 meV with decreasing quantum well width from 19.0 to 2.9 nm. The binding energies of X+ are about 25% smaller than the X− binding energies in the same structures. The magnetic field behavior of X− and X+ binding energies differ qualitatively. With growing magnetic field strength, X− increases its binding energy by 35–150%, while for X+ the binding energy decreases by 25%.