Electron microscopy study has been performed on the microstructure of (100) CdTe epitaxial layers, which were grown upon 4 ˚-off (100) GaAs substrates by metalorganic chemical vapor deposition(MOCVD). The substrates were prepared by etching and washing in DI water. Fine scale substrate surface roughness by etching eliminates the anisotropic defect structure due to formation of high aspect ratio island nuclei and differences in Schmid factor.
The surface of epitaxial later is covered with a large number of elongated pyramidal hillocks along $[01\bar{1}]$ direction. The diagonal line of the elongated pyramid on the surface lie along <011> directions. The hillocks are built up by the propagation of the stacking disorders. Deposition errors make the planar defects to be formed any place as well as on surface irregurities. So hillocks differs in size(＜ 2.5㎛ × 6.5㎛). Growth mediated planar defects are responsible for the formation of elongated pyramidal hillocks in relation to the anisotropic distribution of planar defects-planar defects propagated by a growth mechanism are expected to be found particularly for the $[01\bar{1}]$ direction.
If KOH dissolved in water have been tried as a final substrate rinse instead of DI water, it produced surface with considerably lower hillock densities. Potassium has such a benefit effect on the morphology of the layer grown onto (100) GaAs.
