STRUCTURAL-PROPERTIES OF ZNSE ON GAAS GROWN BY ATOMIC LAYER EPITAXY

ZnSe epilayers were grown on GaAs (100) substrates by atomic layer epitaxy modified from chemical-vapor deposition with thicknesses ranging from 600 to 6000 angstrom. X-ray-diffraction and micro-Raman scattering measurements were carried out to study the effects of strain in the ZnSe epilayers with different thicknesses. The increase in full width at half-maximum of double-crystal x-ray rocking curves was observed for layers thicker than the critical thickness, which indicates that the crystallinity gets strongly degraded when the layers are grown over the critical thickness. The critical thickness estimated by x-ray rocking curves is 1500 angstrom, while that obtained by micro-Raman scattering is 1000 angstrom. This difference suggests that the elastic strain depends on the layer depth for ZnSe epilayers around the critical thickness.