Cubic AlyGa1-yN/GaN heterostructures on GaAS(0 0 1) substrates were grown b
y radio-frequency plasma-assisted molecular beam epitaxy. High resolution X
-ray diffraction, micro-Raman, spectroscopic ellipsometry, and cathodolumin
escence measurements were used to characterize the structural, optical and
vibrational properties of the AlyGa1-yN epilayers. The AlN mole fraction y
of the alloy was varied between 0.07 <y<0.20. X-ray diffraction reciprocal
space maps demonstrate the good crystal quality of the cubic AlyGa1-yN film
s. The measured Raman shift of the phonon modes of the AlyGa1-yN alloy was
in excellent agreement with theoretical calculations. Both SE and CL of the
AlyGa1-yN epilayer showed a linear increase of the band gap with increasin
g Al-content. <(c)> 2001 Elsevier Science B.V. All rights reserved.