High-quality ZnO films have been grown on epi-GaN predeposited on Al2O3 sub
strates using RF-plasma assisted molecular beam epitaxy. The growth conditi
ons to obtain high-quality ZnO films on epi-GaN are Zn-pre-growth treatment
on epi-GaN and two-step growth. RHEED intensity oscillations are observed
from the beginning of ZnO growth on the low-temperature ZnO buffer layer in
dicative of two-dimensional growth. Low-temperature (10 K) photoluminescenc
e of ZnO films grown on epi-GaN shows that the linewidth of the strongest e
mission at 3.3676 eV is as narrow as 1.5 meV, while the deep-level emission
at around 2.3 eV is negligibly small. (C) 2000 Elsevier Science B.V. All r
ights reserved.