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Keywords:

  • ZnS;
  • GaP;
  • critical thickness;
  • reciprocal space map;
  • MBE

Abstract

The lattice-relaxation process of ZnS grown on (001) GaP substrates has been investigated in detail by using high-resolution X-ray diffraction (HRXRD) and transmission electron microscopy (TEM). Reciprocal space maps (RSMs) of 224 XRD peaks for ZnS and GaP clearly show transition from coherent growth to relaxed growth with increasing the thickness. For a 32nm-thick ZnS layer the RSM indicates almost coherent growth to GaP substrate; it also shows, however, a sign of the initiation of lattice relaxation. The cross-sectional lattice image of the 32 nm thick ZnS layer observed by TEM exhibits defects probably resulting from lattice relaxation, while no such defects are seen for the 21 nm thick layer. Therefore, the critical thickness of ZnS on GaP seems to be between 21 nm and 32nm. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)