Observation of Impurities in GaAs by Electron Beam Electroreflectance (EBER)

Using the modulated reflectance technique of EBER, we observe spectral features below the bandgap in high purity GaAs. We ascribe these features to either bound excitonic or impurity-to-band transitions involving electrically active sites in the GaAs. We discuss the energy position, lineshape, and temperature dependence of these features.