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V. Bondarenko, K. Petters, R. Krause-Rehberg, J. Gebauer, H. S. Leipner
Study of vacancy-type defects after Cu diffusion in GaAs
Physica B 308-310 (1-4) (2001), 792-795

Semi-insulating GaAs was contaminated by Cu. For this purpose, a thin Cu layer (30nm) was deposited by evaporation. The diffusion and the homogeneous distribution of the Cu was performed during an annealing step at 1100?C under defined As vapour pressures. The samples were quenched to room temperature. During a subsequent isochronal annealing experiment, vacancy clusters were found to be created, grown, and finally disappeared. The number, size, and distance depend on the annealing temperature and quenching speed. Positron lifetime measurements show that the clusters contain more than 10 vacancies. Moreover, Doppler-coincidence spectroscopy shows clearly that the clusters are surrounded by Cu atoms. The association of Cu-rich precipitates and voids with a diameter of up to 50nm could be evidenced by analytical transmission electron microscopy. The smaller clusters have a crystallographic shape, while larger voids are spherical with a Cu-rich shell. The particles are frequently bound to dislocations. A possible model related to the out-diffusion of copper and the agglomeration of the formed vacancies is discussed.

Keywords: GaAs; Cu diffusion; Vacancy clusters; Positron annihilation; TEM
© Elsevier Physica B

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