We present an approach to the investigation of structural disorder in quant
um wells (QWs) based on the reflectivity line shape analysis of radiatively
coupled QWs. In the case of anti-Bragg structures, as a consequence of the
condition of destructive interference, the reflectivity spectrum is indeed
extremely sensitive to vertical disorder. We exploit the method in the cas
e of GaAs/AlGaAs structures and we demonstrate the possibility of measuring
differences in the excitonic transition energies of the two QWs as small a
s 10% of the inhomogeneous broadening. (C) 1999 American Institute of Physi
cs. [S0003-6951(99)04122-4].