Nonuniform segregation of Ga at AlAs/GaAs heterointerfaces

Segregation at GaAs/AlAs (001) heterointerfaces has been studied experimentally by an in situ electron diffraction technique during molecular-beam epitaxy and by ex situ transmission electron microscopy. Whereas the GaAs-on-AlAs interface is abrupt, we find Ga segregating up to 20 crystal planes when depositing AlAs on GaAs(001). The measurements indicate an anisotropic in-plane structure of this interface with elongated ${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As regions extending along [1-bar10]. Our findings provide insight into both the segregation mechanism and electron diffraction from growing surfaces at glancing angles.