Anisotropic surface morphology in a tensile-strained InAlAs layer grown on InP(100) substrates

Abstract

The anisotropic surface morphology of a tensile-strained In0.42Al0.58As layer grown on an InP(100) substrate was investigated by means of observing the cross-hatch patterns between two orthogonal in-plane directions: [011] and [0 (1) over bar1]. Analysis results using atomic force microscopy evidently reveal a higher array density along direction [011], with an asymmetrically sharp ridge across each array. Conversely, there was a much lower array density along direction [0 (1) over bar1] and a symmetrically big mound-like ridges. Our X-ray diffraction and energy-dispersive spectroscopy analyses showed a more substantial amount of strain relaxation along direction [0 (1) over bar1] due to preferential indium incorporation along [011]. As a result, the big mound ridges over the arrays along direction [0 (1) over bar1] were believed to be the result of local indium accumulation. Additionally, microcrack formations, penetrating into substrates, were exclusively formed on top of the mound ridges with central depressions along direction [0 (1) over bar1], presumably causing additional anisotropic strain relaxation.