THE EFFECT OF DISLOCATIONS ON THE OPTICAL-ABSORPTION OF HETEROEPITAXIAL INP AND GAAS ON SI

The optical absorption of heteroepitaxial InP and GaAs layers grown on exactly [001]-oriented Si substrates was investigated by spectroscopi c ellipsometry combined with anodic stripping. In the wavelength range above the band-gap-equivalent wavelength considerable absorption was found which depends on the dislocation density in the layer. A theoret ical model based on the electric microfield of charged dislocations wa s developed which agrees closely with the experimental results. After calibration differential spectroscopic ellipsometry was used to determ ine the dislocation-density profile in the InP and GaAs layers. Thus, the dislocation density could be determined in the region of a few ten s of nm to the heterointerface of InP on Si where the identification a nd counting of dislocations is impossible by other methods. (C) 1996 A merican Institute of Physics.