Excitons bound to isoelectronic Te traps in ZnSe quantum wells: A theoretical study

A theoretical study is made of excitons and holes bound to a single tellurium (Te) impurity in bulk ZnSe and centered in ZnSe-${\mathrm{Zn}}_{1-x}{\mathrm{Mn}}_x\mathrm{Se}$ strained quantum wells. We use an effective-bond-orbital model for the holes in order to account for the complicated valence-band structure, and the spherical effective-mass approximation to describe the electron. The mutual Coulomb interaction is included, and solutions for the two-body system are obtained using the variational method in an iterative scheme. The strong lattice-relaxation effects present in the binding of the hole to the Te impurity are absorbed in the value for the localized hole-attractive potential at the site of the impurity. This value is determined by fitting the experimental value for the binding energy of the bound exciton. The oscillator strengths, the extension of the bound-exciton wave functions, and the energies of bound holes are then predicted. We observe a discrepancy between the fitted value for the localized impurity potential for the bulk case and the quantum-well case. An experiment to test our explanation for the discrepancy is proposed.