Study of surface roughness using spectral reflectance measurements recorded during the MOVPE of InAs/GaAs heterostructures

InAs layers were elaborated on semi-insulating GaAs (1 0 0) substrates in a horizontal atmospheric pressure MOVPE reactor at a temperature of 450 °C. The growth process was in situ monitored by spectral reflectance (SR) in the wavelength range 200–1100 nm. The best fittings of the experimental responses using the transfer matrix method (TMM) combined with the Bruggeman effective medium approximation (EMA), permit the study of the surface roughness during the growth and the determination of the InAs layer thickness at different phases of the epitaxy. The calculations were in good agreement with the ex situ spectroscopic ellipsometry (SE) measurements. The roughness modeled by an effective layer thickness, obtained indirectly from SR and SE measurements, was well correlated with direct measurements using the atomic force microscopy (AFM). Simulated roughness closely obeys a relationship of the form of deff(SR/SE)≈1.5RMS (AFM) where RMS (AFM) is the root-mean-square roughness measured by AFM.