Effect of Aluminium Composition on the Luminescence of AlAs/AlxGa1-xAs Multiple Quantum Wells

Abstract
The influence of Al composition x on the optical properties of AlAs/Al x Ga1-x As multiple quantum well heteroestructures (MQWH) is studied by photoluminescence (PL) and photoluminescence excitation spectroscopy (PLE) at 2 K. Besides the expected high energy shift of the luminescence lines with increasing Al concentration in the wells, broader PL peaks and larger Stokes shifts between PL and PLE heavy-hole related excitons are observed. A simple model based only on alloy broadening cannot explain these features. We therefore assume that also a progressive deterioration of the interface quality due to an enhanced three dimensional character of the particular growth mode of the ternary Al x Ga1-x As alloy is responsible for the increased linewidth and Stokes shift.