Use of fractal surface parameters for mobility estimation in InSb/GaAs structures

Abstract

InSb-based heterostructures are commonly used for the fabrication of infrared photodetectors, magnetic field sensors, transistors. For the most applications, heterostructures are grown on semi-insulating substrates like Si, GaAs, Ge, which have a large lattice mismatch with respect to InSb. Strain relaxation in heterostructures leads to generation of a large number of microtwins, dislocations, and stacking faults that significantly device performance. Defect interaction in heterostructures leads to formation of an irregular surface microstructure, which is uninformative to characterize by Euclidean geometry. Multifractal approach was used to analyze surface morphology, studied by atomic force microscopy. It was shown that both multifractal parameters of the surface structure: the Rényi entropy and structure order degree are determined by hillocks. Even more surprising was the finding of correlation between multifractal parameters and electron mobility. Analysis of a composition of structural defects showed that the correlation is due to proportionality of density of dislocations and microtwins, which make the main contribution to electron scattering. The study opens up exciting possibilities for controlling electron mobility in heterostructures in which dislocations make a major contribution to electron scattering or their density is proportional to the density of main scattering centers.