Revealing of threading and misfit dislocations in partially relaxed InGaAs/GaAs heterostructures

Both threading and misfit dislocations in partially relaxed InGaAs/GaAs heterostructures with a small lattice-mismatch have been investigated by means of chemical etching and atomic force microscopy (AFM). An anisotropic etching in HF–H2SO4–H2O2 based aqueous solution was successfully used to determine the polarity of the crystallographic surfaces and an ultrasonic-vibration aided etching in CrO3–HF–H2O based solution was employed to reveal threading dislocations on the heterostructure surfaces. AFM measurements of surface morphology of the structures revealed a well-resolved cross-hatch pattern, which reproduced the network of underlying misfit dislocations, and, in addition, the outcrops of threading dislocations on the surface in a form of characteristic craters. Analysis of the results allowed drawing a conclusion on the mechanism of misfit strain relaxation in the investigated heterostructures. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)