XRD characterization of ZnO layers grown on GaAs(111)B, c‐plane and a‐plane sapphire substrates by plasma‐assisted MBE

Abstract

AbstractStructural evaluation of the ZnO epitaxial layers grown by plasma‐assisted molecular beam epitaxy (PAMBE) on the GaAs (111)B, c ‐plane (0001) and a ‐plane (11‐20) sapphire (α ‐Al2O3) substrates was demonstrated by using high‐resolution X‐ray diffraction (XRD). The in‐plane epitaxial relationships between the ZnO layers and the substrates were found to be ZnO(0001)<11‐20>II GaAs(111)<1‐10>, ZnO(0001)<11‐20>IIα ‐Al2O3(0001) <1‐100> and ZnO (0001)<11‐20>II α ‐Al2O3(11‐20)<0001>. All the ZnO layers were highly oriented to the c‐axis but larger fluctuations of the c‐axis were observed for the layers on the GaAs(111)B substrates. The lattice parameters of the ZnO layers were evaluated from the θ ‐2θ and ω ‐2θ scans, and reciprocal lattice mappings (RLMs). The in‐plane compressive strains up to 0.3% in the ZnO layers on both the c ‐plane and a ‐plane sapphire substrates, and the in‐plane tensile strains up to 0.4% in the ZnO films on the GaAs(111)B substrates were observed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)