We present an experimental data, which demonstrate a basically new mechanism of carrier radiative recombination in semiconductor heterostructures-recombination via Tamm-like interface states. Bright line was observed in photoluminescence spectra of periodical ZnSe/BeTe heterostructures at the energies, which correspond to the optical transitions between electron and hole Tamm-like interface states in studied heterosystem. Photoluminescence via Tamm-like interface states was observed for wide range excitation densities in the temperature range from 15K to 160K. It was found that for short-period ZnSe/BeTe heterostructures at low temperatures and at low excitation densities photoluminescence via Tamm-like interface states is much stronger than conventional interband radiative recombination.
Spectral response of lateral optical anisotropy of periodic undoped type-II ZnSe/BeTe heterostructures with nonequivalent interfaces has been studied by spectroscopic ellipsometry. The spectra revealed two types of features corresponding to optical transitions with energies lying in the bandgap. The position of features of the first type does not depend on the heterostructure period. Features of the second type shift toward lower energies with decreasing period of the heterostructure. This behavior is explained in terms of a model taking into account the existence of electronic and hole interface states, as well as of a mixed-type interface state.
Photoluminescence spectra of modulation-doped quantum well structures based on II-VI semiconductors (CdTe/CdMgTe and ZnSe/ZnBeMgSe) were studied in high magnetic fields it the range of 2D electron concentrations of (1-5)x1011 cm-2. The following peculiarities were found at low mangetic fields: (1) linear increase of the photoluminescence energy with increasing magnetic fields, (2) jumps in this dependence at integer filling-factors, (3) periodical changing of Zeeman splitting. The observed behavior are interpreted in a frame of a model which takes into account combined exciton electron recombination processes in the presence of magnetic fields.