Positively and Negatively Charged Trions in ZnSe-Based Quantum Wells

Abstract

Excitons and charged excitons (trions) are investigated in ZnSe-based quantum well structures with (Zn,Be,Mg)Se and (Zn,Mg)(S,Se) barriers by means of magneto-optical spectroscopy. Binding energies of negatively (X−) and positively (X+) charged excitons are measured as functions of quantum well width, free carrier density and in external magnetic fields up to 47 T. The binding energy of X− shows a strong increase from 1.4 to 8.9 meV with decreasing quantum well width from 19.0 to 2.9 nm. The binding energies of X+ are about 25% smaller than the X− binding energies in the same structures. The magnetic field behavior of X− and X+ binding energies differ qualitatively. With growing magnetic field strength, X− increases its binding energy by 35–150%, while for X+ the binding energy decreases by 25%.