Epitaxial growth of non-polar a-plane A1N films by low temperature sputtering using ZnO buffer layers

摘要

This article presents an investigation on the epitaxial growth of non-polar a-plane A1N thin films by low temperature sputtering using ZnO buffer layers. Prior to the deposition of the A!N films, epitaxial growth of a-plane ZnO thin films on r-plane sapphire substrates was performed by a metalorganic chemical vapor deposition (MOCVD). The effect of MOCVD growth conditions on surface morphology and crystallinity of ZnO epi-layer was examined to optimize the growth process of buffer layer. The resulting ZnO epi-layers were used as buffer layers to grow non-polar A1N by low temperature sputtering. The measurements of XRD 2theta/ omega- and phi-scans indicate that the epitaxial relationship among AIN, ZnO and sapphire substrate is (ll20) _AIN//(1120)_ZnO //(lT02) and (1100)_AIN //[1100]_ZnO //[ll20]_Al_2O3 . Cross-sectional transmission (1100)_AIN //[1100]_ZnO //[ll20]_Al_2O3 and(1100)_AIN //[1100]_ZnO //[ll20]_Al_2O3 cross-sectional transmission electron microscopy (XTEM) revealed that no reactive intermediate layers formed at the interfacial region between AIN film and ZnO buffer layer. The a-plane ZnO layers can be used as lattice matched templates for epitaxial growth of non-polar AIN by low temperature sputtering.