Investigation of Surface Defects in AlInSb Metamorphic Buffer (MB) Grown on GaSb

We have conducted an investigation of the different surface defects observed on InAlSb metamorphic buffers grown on GaSb. There are two different defect modes found in this system: crystallographic surface features and surface cross-hatching. We have characterized both defect modes using optical microscopy, scanning electron microscopy, and plan-view and cross-sectional transmission electron microscopy. It is found that particulates from polishing slurry or incomplete oxide desorption on the substrate before the growth are the root of the crystallographic defects. Surface crosshatching is shown to be caused by the coalescence of strained islands formed at the onset of buffer layer growth. Despite the presence of these defects, we have shown that substantial areas of the surface are defect-free and can be effectively used for realizing devices on this platform. Threading dislocation and crystallographic defect densities are found to be ∼1 × 107/cm2 and ∼5 × 104/cm2, respectively.