DETERMINATION OF THE CHEMICAL VALENCE-BAND OFFSET FOR ZN1-XMNXSE ZNSEMULTIPLE-QUANTUM-WELL STRUCTURES OF HIGH-X/

Six Zn1-xMnxSe/ZnSe multiple-quantum-well structures with barrier Mn c oncentrations of x approximate to 0.25 were studied by reflectivity sp ectroscopy, photoluminescence excitation. spectroscopy, and spin-flip Raman spectroscopy at low temperatures and at magnetic fields up to 7. 5 T. The three techniques give complementary information about the exc itonic and electronic transitions in the quantum wells and in the barr ier layers. In analyzing the spectra we have focused on three quantiti es whose behavior is sensitive not only to the chemical valence-band o ffset (VBO) fraction but also to the strain and to the interface quali ty. These three quantities are the energy splitting between the first light and heavy-hole quantum-well transitions in zero-magnetic field, the energy splitting between the two polarization components of the fi rst heavy-hole quantum-well transition at 3 T and the saturation Raman shift for spin-flip scattering in the conduction band of the quantum well. All three quantities were calculated as functions of well width and compared with the values obtained by experiment to determine the V BO for the Zn1-xMnxSe/ZnSe system for x approximate to 0.25. In our mo del, we take into account the strain, the exciton binding energy effec ts and the interface roughness, as well as the enhanced paramagnetism at the interfaces. A consistent description of the experimental data c an only be achieved by taking a VBO of (20 +/- 10)%, combined with a b iaxial strain of the structure to a lattice constant a(L) = (a(ZnSe) 2a(ZnMnSe))/3 and with an interface roughness represented by average Mn concentrations of 0.9x and 0.1x in the cation monolayers immediatel y adjacent to the interface between the barrier and the quantum well, respectively.