We investigated the epitaxy and morphology of GaAs/Ge superlattices grown by metal organic chemical vapor deposition (MOCVD) under a range of conditions. The surfaces of Ge layers deposited on GaAs at 650 degrees C and 100 Torr are observed to be rough in cross-sectional transmission electron microscopy. When either the temperature is lowered to 500 degrees C or the pressure is increased to 250 Torr, the surface of the first deposited Ge layer is observed to be smooth. This behavior suggests that Ge roughening is a thermodynamically favorable process that can be kinetically limited with appropriate growth conditions. At 500 degrees C, GaAs islands on Ge do not completely coalesce into one film. This may result from poor surface coverage; the short depositions would not be sufficient to coarsen and completely coalesce the islands. At 650 degrees C, growth on offcut substrates did not suppress antiphase boundaries, likely due to the unique conditions for GaAs/Ge superlattice growth. A wide-range of two- and three-dimensional nanostructures are formed and should allow insight in structure-property correlations in semiconducting thermoelectric materials. (C) 2015 Elsevier B.V. All rights reserved.