Characterization of InP/GaInAs superlattices by spectroscopic ellipsometry

A set of InP/GaInAs 30 periods superlattices with a wide range of barrier and well thicknesses were grown on (100) InP substrates by metal organic vapor phase epitaxy (MOVPE). Their optical response was measured at room temperature by spectroscopic ellipsometry from 1.8 to 5 eV. The nominal structures were checked by two methods of multi-layer modelling: full simulation using bulk dielectric functions for each layer and effective medium approximation, with the appropriate volume fractions. The thicknesses of well, barrier, and oxide overlayer were determined, and the effects of the interface region were discussed. The dielectric functions derived from the measured tg (psi) and cos(Delta) spectra were compared with the simulated ones obtained from the fitted structural model.