Line-of-sight mass spectrometric study of As/Sb exchange on Sb-terminated and Ga-terminated GaSb (001) during molecular beam epitaxy

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Abstract
Rates and total amounts of the arsenic for antimony exchange reaction on the GaSb (001) surface are measured via line-of-sight mass spectrometry during molecular beam epitaxial growth. On the Sb-terminated GaSb (001) surface, an As for Sb exchange is observed to occur at all levels of incident As2 flux studied. By contrast, on the surface with one monolayer of Ga, there exists a critical As2 flux below which the As for Sb exchange is suppressed, and a two-dimensional (2D) surface morphology is maintained. Above the critical As2 flux, the As for Sb exchange is observed to be linear with increasing As2 flux. Substrate temperatures above 470 °C and As2 fluxes greater than 1×10−6 Torr beam flux pressure lead to a drastic increase in As/Sb exchange accompanied by the occurrence of 3D surface morphology. As/Sb exchange at the interfaces of InAs/GaSb type-II superlattices leads to a reduced average lattice constant of the superlattices and degrades interface quality, as determined by x-ray diffraction.