Photoluminescence and excitation spectra of Zn1−xMnxSe films and superlattices grown by molecular-beam epitaxy

Measurements of photoluminescence and photoluminescence excitation spectra at liquid helium temperatures are presented for films of ZnSe, Zn1−xMnxSe (0≤x≤0.33), and multilayer structures ZnSe/Zn1−xMnxSe (x=0.23, 0.33, and 0.51) grown by molecular-beam epitaxy. All samples investigated had the zinc-blende structure. The temperature dependence of the luminescence from the superlattices has been studied up to 300 K. Good quality of the samples is evidenced by the reduction of impurity- or defect-related long wavelength emissions. Several new features in the photoluminescence spectra were resolved (e.g., a region of low-intensity luminescence ending with a sharp cut off at about 75 meV above the main line) which were not observable in bulk samples. The presence of internal strains in the epitaxially grown superlattice samples results in the observed splitting of the heavy- and light-hole valence bands. Furthermore, the strain present can actually dominate over the quantum confinement to produce a net red shift of the near band-edge features. Both the red shifts and the heavy-to-light-hole band splitting are consistent with the estimates of the lattice mismatch-induced strains.