The effect of dislocations on the optical absorption of heteroepitaxial InP and GaAs on Si

Abstract

The optical absorption of heteroepitaxial InP and GaAs layers grown on exactly [001]-oriented Si substrates was investigated by spectroscopic 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 theoretical model based on the electric microfield of charged dislocations was developed which agrees closely with the experimental results. After calibration differential spectroscopic ellipsometry was used to determine the dislocation-density profile in the InP and GaAs layers. Thus, the dislocation density could be determined in the region of a few tens of nm to the heterointerface of InP on Si where the identification and counting of dislocations is impossible by other methods.