VALENCE-BAND PARAMETERS AND G-FACTORS OF CUBIC ZINC SELENIDE DERIVED FROM FREE-EXCITON MAGNETOREFLECTANCE

Reflectance spectra were measured on cubic ZnSe crystals in magnetic fields up to 18 T and transverse energies of the 1s-exciton states derived by a line-shape fit. The results are analyzed combining the existing low-field theory of Γ6-Γ8 exciton states with the results of variational calculations for excitons in polar materials without valence-band degeneracy. The observed linear Zeeman splitting yields a conduction-band electron g factor gc=1.37±0.25, an effective hole g factor κ=-0.21±0.06, corresponding to κ=-0.28±0.08, and an upper limit for the short-range electron-hole spin exchange 2Δ10.1 meV. From the 1s-2s exciton-state energy separation we derive the exciton Rydberg R0*=16.8±0.4 meV and obtain E1s=17.4±0.4 meV exciton binding energy. The observed diamagnetic-shift rates yield an exciton reduced mass μ0*m0=0.095±0.003 corresponding to γ1*=4.3±0.5 for me*m0=0.16. We further determine γ2*=0.59±0.07 and γ3*=1.34±0.30. The bare valence-band parameters γi derived from the renormalized parameters γi* are γ1=4.8±0.6, γ2=0.67±0.08, and γ3=1.53±0.35. With the parameters derived, energy shifts and splittings of exciton states not used for the evaluation of the parameters are calculated in good agreement with the experimental results. The exciton reduced mass derived from diamagnetic-shift rates yields an exciton Rydberg in good agreement with the Rydberg obtained from the 1s-2s exciton-state energy separation. Finally, the energy separations of 2p-exciton states calculated from our parameters are in close agreement with two-photon absorption measurements. This is taken as a justification for the theoretical model applied and suggests the derivation of fundamental parameters of related compounds such as CdTe or ZnTe along similar lines. © 1979 The American Physical Society.