We have observed the suppression of Fano resonances in epitaxial layer
s of GaAs in a magnetic field due to discretization of the quasi-conti
nuum by quantum confinement. Our observations can be explained using a
simple ''picket fence'' model in which the density of states can be a
djusted to model the different thickness epitaxial layers. The suppres
sion of the Fano resonance occurs for length scales which are unusuall
y large for optical experiments.