Optical determination of interface roughness in multilayered semiconductorstructures

We have developed a new approach (the LQR method) for calculating the refle ctivity and transmission spectra of a multilayer optical material with N in terfaces, as an alternative to the matrix method. The approach allows the i nclusion of the effects of interface roughness by introducing a "rough" ele ment between adjacent layers. For this purpose we have developed an empiric al model, which describes the effect of interface roughness on an optical b eam passing through or being reflected from an interface. An assessment of the interface roughness of a multilayer structure was carried out by fittin g the experimental reflectivity spectrum of GaAs/AlGaAs multiple quantum we ll samples with and without oxidation of the barrier layers. The refractive index and the thickness of the oxidised layers were also obtained from the fit.