Photoluminescence topography of shallow impurities in GaAs epilayers grown by metalorganic vapor phase epitaxy.

Spectrally and spatially resolved low-temperature photoluminescence topography has been applied to investigate the lateral variation of impurities in nominally undoped epitaxial GaAs layers. The concentrations of both shallow donors and acceptors exhibit lateral variations. The donor variation pattern appears to be arbitrary, but the fluctuation of shallow acceptor carbon clearly reproduces the well-known cellular structure of the liquid encapsulated Czochralski GaAs substrate dislocation density distribution, suggesting that the carbon incorporation into the epitaxial layer is influenced by the substrate during the growth of metalorganic vapor phase epitaxy.