Parameters influencing interfacial morphology in GaAs/Ge superlattices grown by metal organic chemical vapor deposition

Publication date: 1 February 2016
Source:Journal of Crystal Growth, Volume 435
Author(s): Roger Jia, Eugene A. Fitzgerald
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°C and 100Torr are observed to be rough in cross-sectional transmission electron microscopy. When either the temperature is lowered to 500°C or the pressure is increased to 250Torr, 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°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°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.



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