Study of composition and critical-point broadening in InAs/Ga(1-x)In(x)Sb superlattices using spectroscopic ellipsometry

InAs/(GaIn)Sb superlattices (SL) grown by solid-source molecular-beam epitaxy were studied by spectroscopic ellipsometry. The pseudodielectric function of InAs/GaSb SLs could be fitted using modified bulk dielectric functions of InAs and GaSb with pronounced energy shifts and broadening of critical-point resonances. These changes in the dielectric functions of the constituent layers can be explained only in part by pseudomorphic strains, therefore providing evidence for thin-layer critical-point broadening and quantum confinement effects. For InAs/(GaIn)Sb SLs, the extremum in the pseudodielectric function derived from the E1 critical point of (GaIn)Sb was found to shift to lower energies with increasing In content, and thus can be used as a probe for the composition of the (GaIn)Sb SL layers.