K. Tillmann and M. Luysberg
Institut für Mikrostrukturforschung

The structural degeneration of interfaces in AlAs/GaAs:Be heterostructures epitaxially grown at low temperatures has been analysed by high-resolution transmission electron microscopy. Numerical data on the layer stoichiometry ob-tained by the quantitative analysis of high-resolution micrographs are used to calculate diffusion parameters control-ling the exchange of aluminium and gallium atoms. Analyses demonstrate that beryllium doping of the GaAs layers decreases the interfacial mixing by up to one order of magnitude and results in an activation enthalpy enhanced by about 0.5 eV compared to the undoped heterostructures. The results lead to the conjecture that the diffusion process is governed by the defect related electronic properties close to the interfaces or the formation of defect complexes rather than by the pure concentration of gallium vacancies.