Observation of shallow residual donors in high purity epitaxial GaAs by means of photoluminescence spectroscopy

We report the first observation of three different residual donors in undoped high purity vapor phase epitaxial GaAs using the high resolution photoluminescence spectroscopy technique at temperatures ～ 2 K. The binding energies of these shallow donors were determined from the excited state transitions of excitons bound to neutral donors and they are found to be in very good agreement with corresponding values obtained from high-resolution far infrared Fourier transform spectroscopy, using the modulated photoconductivity technique.