Study of sublattice orientation of GaAs on Ge

High crystalline quality GaAs/Ge/GaAs heterostructures have been grown on both straight and slightly misoriented GaAs(100) substrates by molecular beam epitaxy. High-energy electron diffraction was used to study the sublattice rotation of GaAs on epitaxial Ge dependent on the use of a Ga or As prelayer. On straight (100) substrates, a Ga prelayer was observed to rotate the GaAs surface reconstruction by π/2 while an As prelayer preserved the GaAs orientation observed prior to Ge deposition. No rotation of the surface was observed on substrates tilted 4° towards [011]. We present a growth model to explain these results.