Raman spectroscopy of impurities in GaAs

Raman spectroscopy is sensitive to impurities in semiconductors either via light scattering by internal electronic excitations of the impurity or via scattering by impurity induced local vibrational modes (LVM). Both types of scattering have been used successfully to study impurities in GaAs. To illustrate this Raman scattering by shallow acceptors is dicussed as an example for scattering by electronic excitations. It can be used as a quantitative tool for the assessment of residual impurities in bulk GaAs substrate material. Raman scattering by LVM is discussed for highly Si or Be doped epitaxial GaAs layers. From the analysis of the LVM spectrum of, e. g., Si in GaAs insight is gained into the site distribution of the dopant atoms. Based on the high sensitivity of this Raman technique it is also possible to study the incorporation of dopants atoms in a single delta- (or planar) doped layer.