No abstract

No abstract

Using reflection, photoluminescence and excitation spectroscopy we carried out systematic studies on the optical properties in the excitonic energy region of ZnTe/GaAs epilayers grown by hot-wail epitaxy (HWE). We calculate t h e strain magnitude, the light-hole (Ih) and heavy-hole (hh) energy shifts, and compare t h e theoretical values with t h e experimentally observed energy positions in ZnTe films of different thicknesses. The detected energy distance between the free excitons X,, and X, , decreases with increasing layer thickness, indicating a relaxation of the thermally induced strain in t h e ZnTe layer. Additionally, w e investigate the incorporation of different impurities, the electronic structure of the main acceptor-exciton complexes (A', X) and the high-photon-density spectra of the ZnTe films. For increasing densities a biexciton band appears, and we determine the biexciton binding energy to amount to about 3.3 f 1.0 meV.

No abstract

We determine the electronic structure of t h e dominant donor-exciton complex (Do, X) in high-quality ZnSeIGaAs epilayers grown by molecular beam epitaxy. Besides the recombination line i2 from the ground state of t h i s complex, a set of further lines, called 12i (i = a , . . . , e), was observed in luminescence and excitation spectroscopy. They represent transitions into (or from) excited states (Do, X):of the same exciton complex which are described by single-hole excitation with different hole quantum numbers n , 1. Additionally, strong resonant electronic Raman scattering (RRS) occurs at these donor-bound exciton states. Several scattering lines S,; with non-constant Stokes shifts are identified as involving (DO, X) complexes with varying binding energies as resonant intermediate states. This phenomenon is explained by the strain influence in ZnSeIGaAs for different layer thicknesses, although t h e incorporation of different donor impurities may also contribute to t h e variations of the Stokes shifts