On the mechanism of cross-hatch pattern formation in heterostructures with a small lattice mismatch

The mechanism of cross-hatch (CH) pattern formation on the surface of GaMnAs/InGaAs/GaAs (001) heterostructures with a small lattice mismatch, related to the peculiarities of glide process of dislocations in epilayers, is considered. Electrically active defects in these heterostructures and the surface morphology of epilayers were investigated by electron beam induced current imaging, transmission electron microscopy (TEM), atomic force microscopy and differential interference contrast microscopy in combination with selective chemical etching. The studies revealed a high-density system of extended defects (EDs) in the bulk of InGaAs epilayers in addition to misfit dislocations at the epilayer/substrate interface. These defects possess a number of properties reflecting their unusual core structure: pronounced crystallography, recombination activity, existence of elastic strains in the core, and at the same time the absence of contrast in the TEM images. Model experiments performed on InGaAs epilayers give grounds to consider that the revealed EDs are similar in properties to a new type of EDs generated by moving dislocations in plastically deformed Si and SiGe crystals. The formation of CH surface structure is assumed to be directly related to the emergence of the EDs during the strain relaxation process in heterostructures based on III-V and IV-group materials.