Correlation between atomic-scale structure and mobility anisotropy in InAs/Ga1-xInxSb superlattices

We have performed detailed characterization of atomic-scale interface structure in InAs/Ga(1-x)ln(x)Sb superlattices using cross-sectional scanning tunneling microscopy (STM) and established a semiquantitative correlation between interface structure and transport properties in these structures. Quantitative analysis of STM images of both (110) and (1 (1) over bar 0) cross-sectional planes of the superlattice indicates that interfaces in the (1 (1) over bar 0) plane exhibit a higher degree of interface roughness than those in the (110) plane and that the Ga1-xInxSb-on-InAs interfaces are rougher than the InAs-on-Ga1-xInxSb interfaces. The roughness data are consistent with anisotropy in interface structure arising from anisotropic island formation during growth and, in addition, a growth-sequence-dependent interface structure arising from differences in interfacial bond structure between the two interfaces. Low-temperature Hall measurements performed on these samples demonstrate the existence of a substantial lateral anisotropy in mobility that is in semiquantitative agreement with modeling of interface roughness scattering that incorporates our quantitative measurements of interface roughness using STM.