Exciton binding energy in (Al,Ga)As quantum wells: Effects of crystal orientation and envelope-function symmetry

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Abstract
We report the first observation of 2s-excitonic features in the luminescence of non-(001)-oriented (Al,Ga)As multiple-quantum-well structures and conclude that the heavy-hole excitonic binding energy does not depend significantly on the orientation of the quantum well in the crystalline lattice. This is substantiated by calculations showing only minor changes (∼0.3 meV) in the binding energy for the lowest heavy-hole exciton. However, a 10% anisotropy is predicted for the light-hole exciton, which is caused by mixing with the nearby second heavy-hole exciton.