In-Plane Orientation and Polarity of ZnO Epitaxial Films on As-Polished Sapphire (α-Al 2 O 3 ) (0001) Substrates Grown by Metal Organic Chemical Vapor Deposition

• Published in: Japanese Journal of Applied Physics 2003-03, Vol.42 (Part 2, No. 3B), p.L264-L266
• Main Authors: Zhang, Bao-ping, Manh, Le-hong, Wakatsuki, Katsuki, Tamura, Kentaro, Ohnishi, Tsuyoshi, Lippmaa, Mikk, Usami, Noritaka, Kawasaki, Masashi, Koinuma, Hideomi, Segawa, Yusaburo
• Format: Article
• Language: English
• ISSN: 0021-4922
• DOI: 10.1143/JJAP.42.L264

Authors report the control of the in-plane orientation of ZnO epitaxial films grown on as-polished sapphire (a-Al2O3) (0001) substrates by MOCVD. When passing certain flows of Zn-precursor over the substrate before introducing O-precursor at certain substrate temperatures, unit cells of the ZnO film show the same in-plane orientation as the substrate. Otherwise, 30 degrees rotation is observed between unit cells of ZnO and the substrate. In case of using dietylzinc (DEZn) and O gas as precursors, the substrate temperature and the flow rate of DEZn, under which no-twist ZnO films can be obtained, are determined experimentally. Measurements by coaxial impact collision ion scattering spectroscopy, however, demonstrate that the ZnO films all have +c polarity, regardless of their in-plane orientation. This is different from the results obtained by laser-MBE by which +c polarity on as-polished sapphire (0001) substrates are hardly obtained. Since the +c polarity film is preferable in applications of wurtzite semiconductors, results reveal that MOCVD technique isimportant in future applications of ZnO-related oxides. 13 refs.