Nonintentionally doped AlxGa1-xAs layers with 0.38 less than or equal to x
less than or equal to 0.84 were grown on (100) GaAs substrates by liquid ph
ase epitaxy (LPE) under near-equilibrium conditions. The crystalline qualit
y of the samples was studied by photoluminescence at 2 K and room temperatu
re Raman spectroscopy. The peculiar behavior in the photoluminescence inten
sities of the indirect bound exciton line and the donor-acceptor pair trans
ition is explained from the evolution of the silicon donor binding energy a
ccording to the aluminum composition. It was also possible to observe the e
xcitonic transition corresponding to the AlxGa1-xAs/GaAs interface, despite
the disorder and other factors which are normally involved when growing hi
gh-aluminum-content layers by this technique. Furthermore, Raman measuremen
ts show the quadratic variations of longitudinal optical phonon frequencies
with aluminum concentration in good agreement with previous experimental r
esults. In this work we show that high quality indirect-gap AlxGa1-xAs samp
les can be grown by LPE under near-equilibrium conditions. (C) 1999 America
n Institute of Physics. [S0021-8979(99)00413-2].