Competitive evolution of the fine contrast modulation and CuPt ordering in InGaP/GaAs layers

We use transmission electron microscopy to characterize the morphology of InGaP epitaxial layers grown by metal-organic vapor-phase epitaxy over misoriented GaAs (001) substrates, with a cutoff angle in a range from 0 degrees to 25 degrees. The occurrence of phase separation and CuPt-type ordered superstructures has been observed. The most ordered configuration has been found to appear in layers grown on 2 degrees off substrates, and the strength of order decreases with increasing the misorientation angle beyond alpha=2 degrees. Conversely, whereas the phase separation is less evident in the layer grown at 2 degrees, the sample grown with a misorientation of 25 degrees exhibits the most phase separated configuration. The completion between these two phenomena is discussed depending on the misorientation angle. (C) 1996 American Institute of Physics.