Spectroscopic ellipsometry for characterization of InAs/Ga(1-x)In(x)Sb superlattices

The pseudodielectric function of InAs/Ga(1-x)InxSb superlattices (SLs) grown by solid-source molecular-beam epitaxy, was measured by spectroscopic ellipsometry (SE) for photon energies ranging from 1.2 to 5 eV. The width of the extrema in the SL pseudodielectric function derived from the E1 and E1 + delta1 interband transitions of the SL constituents InAs and Gal(1-x)InxSb, was found to depend on the structural quality of the SL. Differences in the SL quality caused by different sequences of InSb-like and GaAs-like interfaces, were easily detected by SE. The formation of the intended interface alternations was verified by Raman spectroscopy. The extrema in the SL pseudodielectric function originating from the E1 and E1+ delta1 interband transitions of Ga(1-x)InxSb were found to shift to lower energies with increasing In content x. Finally SE has been applied to the analysis of a complete InAs/Ga(1-x)InxSb SL detector structure.