Effects of As-2 versus As-4 on InAs/GaSb heterostructures: As-for-Sb exchange and film stability

We have used cross-sectional scanning tunneling microscopy and x-ray diffra ction to characterize and compare the effects of As-2 versus As-4 on the gr owth of InAs/GaSb heterostructures by molecular beam epitaxy. When GaSb sur faces are exposed to an As-2 flux, the As exchanges with the surface Sb in an anion exchange reaction that creates layers of GaAs. In contrast, when G aSb surfaces are exposed to As-4 fluxes, there is no evidence of the As-for -Sb exchange reaction. When comparing the use of As-2 and As-4 in periodic InAs/GaSb superlattices, the differences in the As incorporation rate into GaSb is further evident in x-ray diffraction spectra as a shift in the aver age lattice constant of the epilayer due to GaAs bond formation. Although i nhibiting the exchange reaction would be useful in the minimization of the cross incorporation of As in the GaSb layers, the growth of InAs/GaSb heter ostructures using As-4 can be complicated by the introduction of film insta bilities that have not been observed in growths using As-2.