Influence of Ga vs As prelayers on GaAs/Ge growth morphology

The surface morphology of GaAs films grown on Ge substrates is studied by scanning force microscopy. We find a dramatic difference arising from Ga as opposed to As prelayers in the formation of anti-phase boundaries (APBs), surface features near threading dislocations, and surface roughness, for films as thick as 1 mu m. Ga prelayer samples are smooth; thin films display some APBs with predominantly one growth domain while the 1 mu m thick film displays the morphology of a homoepitaxial GaAs film. In contrast, As prelayer samples are rough with complicated APE structures, which can be attributed to the increase in single steps during As-2 deposition.