Effect of Substrate Orientation on the Growth Rate and Surface Morphology on GaSb Grown by Metal-Organic Vapor Phase Epitaxy

MOVPE of GaSb grown on (100), (111)A and (111)B GaSb substrates were investigated to study the effect of substrate orientation on the growth rate and surface morphology. Besides growth temperature and V/III ratio, the GaSb growth rate strongly depends on the crystallographic orientation. As the V/III ratio rises, the growth rate on the (111)B oriented substrate decreases, whereas that on the (111)A oriented substrate increases. The surface morphology on different substrates was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). On (111)A substrates, triangular hillocks are the dominant defects, while on (111)B planes, three distinct types of hexagonal hillocks are observed, namely, non-flat top hexagonal structure with spiral growth features (Type I), flat top structure with lateral growth features (Type II), and non-flat top hexagonal structure with multiple islands (Type III). For all types, the basal edges of each hillock are preferentially aligned along directions. A closer look reveals that the top surface of Type II feature consists of many levels of small hexagonal shaped terraces, with each step height in the monolayer range, indicating a step flow growth involved.