Control of polarity of ZnO films grown by plasma-assisted molecular-beam epitaxy: Zn- and O-polar ZnO films on Ga-polar GaN templates

Hong, Soon-Ku; Soon-Ku Hong; Hanada, Takashi; Ko, Hang-Ju; Hang-Ju Ko; Chen, Yefan; Yefan Chen; Yao, Takafumi; Imai, Daisuke; Araki, Kiyoaki; Shinohara, Makoto
November 2000
Applied Physics Letters;11/27/2000, Vol. 77 Issue 22
Academic Journal
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 unipolar (Ga-polar) GaN epilayers are selectively grown. Polarity of ZnO films is evaluated by coaxial impact collision ion scattering spectroscopy. Zn preexposure prior to ZnO growth results in Zn-polar ZnO films (Zn face), while O-plasma preexposure leads to the growth of O-polar ZnO films (O face). High-resolution transmission electron microscopy reveals the formation of an interface layer between ZnO and GaN epilayers in O-plasma preexposed samples, while no interface layer is observed in Zn preexposed samples. The interface layer is identified as single crystalline, monoclinic Ga[sub 2]O[sub 3]. We propose models for interface configurations at ZnO/GaN heterointerfaces, which can successfully explain the different polarities of the ZnO films. © 2000 American Institute of Physics.


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