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

O. Yastrubchak 2Elżbieta Lusakowska 2A. Morawski 2O. Demchuk 1Tadeusz Wosiński 2

1. Polish Academy of Sciences, Institute of Physical Chemistry, Kasprzaka 44/52, Warszawa 01-224, Poland
2. Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland

Abstract

We have investigated MBE-grown InGaAs/GaAs heterostructures with a small lattice-mismatch that contained a net of well-resolved 60O misfit dislocations at the (001) interface. The misfit dislocations are accompanied by threading dislocations, which propagate into the epitaxial layer up to the surface. Atomic force microscopy (AFM) was used to examine an undulating and cross-hatched surface morphology of the heterostructures associated with the threading and misfit dislocations. The dislocations under investigation differ in their core structures. In the predominated glide set configuration the two dislocation types, referred to as α and β, are aligned along two orthogonal [-110] and [110] directions, respectively, at the interface. In order to distinguish between the nonequivalent <110> crystallographic directions on the (001) face of heterostructures we have utilized wet etching of the heterostructures in H2SO4:HF:H2O2 solution. Additionally, an ultrasonic-vibration aided etching in CrO3-HF aqueous solution was used to reveal the terminations of threading dislocations at the surfaces of the structures.
From analysis of the cross-hatched surface morphology of the structures we revealed an asymmetry in the formation of the two types of underlying misfit dislocations resulting from the difference between their glide velocities. Moreover, the obtained results allowed to draw the conclusion that relaxation of epitaxial layers in heterostructures with a small lattice-mismatch is realized in the model of Matthews and Blakeslee who considered the development of interfacial misfit dislocations from pre-existing threading segments driven by the misfit stress against their line tension.

 

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Presentation: poster at E-MRS Fall Meeting 2003, Symposium C, by O. Yastrubchak
See On-line Journal of E-MRS Fall Meeting 2003

Submitted: 2003-06-17 15:26
Revised:   2009-06-08 12:55