Material properties of compositional graded In_xGa_1-xAs and In_xAl_1-xAs epilayers grown on GaAs substrates

The residual strain crystallographic tilt, and surface topography of In_xGa_1-xAs and In_xAl_1-xAs (0<x<0.3) epilayers grown on GaAs substrates are investigated. The residual strain of the In_xAl_1-xAs grown on graded In_yAl_1-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 temperatures 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.