Material properties of compositional graded InxGa1-xAs and InxAl1-xAs epilayers grown on GaAs substrates

The residual strain, crystallographic tilt, and surface topography of InxGa1-xAs and InxAl1-xAs (0<x<0.3) epilayers grown on GaAs substrates are investigated. The residual strain of the InxAl1-xAs grown on graded InyAl1-yAs is shown to be strongly dependent on the thickness of the underlying-graded buffer layers and is larger than that of the InGaAs of the same structure. The crystallographic tilt of the InGaAs epilayers with respect to GaAs substrate is found to be strongly dependent on the growth temperature as well as the layer structure of the underlying buffer layer, while that of InAlAs is insensitive to these two factors. This behavior is attributed to the different roughness of the growth front between these two material systems and is consistent with the observation by atomic force microscopy. (C) 1996 American Institute of Physics.