Xj. Wang et al., Thickness dependence of exciton and polariton spectra from ZnSe films grown on GaAs substrates, J APPL PHYS, 90(12), 2001, pp. 6114-6119
ZnSe films with thicknesses from 0.05 to 1.45 mum were grown on GaAs substr
ates by molecular beam epitaxy. Low temperature photoluminescence (PL) and
reflectance spectra are presented to show the thickness dependence of the e
xciton and polariton properties in the films. In addition to sharp PL peaks
from free and donor bound excitons, an acceptor bound exciton peak was obs
erved in the thin films and its intensity decreases rapidly with the film t
hickness. The PL characteristics show the acceptor centers being the defect
states near the ZnSe/GaAs interface. The classical theory of exciton-polar
itons was used to calculate the reflectance spectra and compared to the mea
sured results. The comparison reveals the effects of strain, surface, and i
nterface on the reflectance spectra from both heavy- and light-hole exciton
s. In addition to the strain-induced light- and heavy-hole splitting, the l
ight-hole excitons show a larger damping and less sensitivity to the surfac
e dead layer than the heavy-hole excitons. When the film thickness increase
s, the interference effects become more important and the contribution from
the excited exciton states to the reflectance spectra may no longer be neg
ligible. (C) 2001 American Institute of Physics.