Sk. Hong et al., Control of polarity of ZnO films grown by plasma-assisted molecular-beam epitaxy: Zn- and O-polar ZnO films on Ga-polar GaN templates, APPL PHYS L, 77(22), 2000, pp. 3571-3573
We report on the growth of polarity-controlled ZnO films by plasma-assisted
molecular-beam epitaxy. Different polar (Zn- and O-polar) ZnO films on uni
polar (Ga-polar) GaN epilayers are selectively grown. Polarity of ZnO films
is evaluated by coaxial impact collision ion scattering spectroscopy. Zn p
reexposure prior to ZnO growth results in Zn-polar ZnO films (Zn face), whi
le O-plasma preexposure leads to the growth of O-polar ZnO films (O face).
High-resolution transmission electron microscopy reveals the formation of a
n interface layer between ZnO and GaN epilayers in O-plasma preexposed samp
les, while no interface layer is observed in Zn preexposed samples. The int
erface layer is identified as single crystalline, monoclinic Ga2O3. We prop
ose models for interface configurations at ZnO/GaN heterointerfaces, which
can successfully explain the different polarities of the ZnO films. (C) 200
0 American Institute of Physics. [S0003-6951(00)02149-5].