STUDY OF COMPOSITION AND CRITICAL-POINT BROADENING IN INAS GA1-XINXSBSUPERLATTICES USING SPECTROSCOPIC ELLIPSOMETRY/

InAs/(GaIn)Sb superlattices (SL) grown by solid-source molecular-beam epitaxy were studied by spectroscopic ellipsometry. The pseudodielectr ic function of InAs/GaSb SLs could be fitted using modified bulk diele ctric functions of InAs and GaSb with pronounced energy shifts and bro adening of critical-point resonances. These changes in the dielectric functions of the constituent layers can be explained only in part by p seudomorphic strains, therefore providing evidence for thin-layer crit ical-point broadening and quantum confinement effects. For InAs/(GaIn) Sb SLs, the extremum in the pseudodielectric function derived from the E(1) 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 co mposition of the (GaIn)Sb SL layers. (C) 1997 American Institute of Ph ysics.