Self-diffusion in Ga69Sb121/Ga71Sb123 isotope heterostructures

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Abstract
Gallium and antimony self-diffusion experiments have been performed in undoped 69Ga121Sb/71Ga123Sb isotope heterostructures at temperatures between 571 and 708 °C under Sb- and Ga-rich ambients. Ga and Sb profiles measured with secondary ion mass spectrometry reveal that Ga diffuses faster than Sb by several orders of magnitude. This strongly suggests that the two self-atom species diffuse independently on their own sublattices. Experimental results lead us to conclude that Ga and Sb diffusion are mediated by Ga vacancies and Sb interstitials, respectively, and not by the formation of a triple defect proposed earlier by Weiler and Mehrer [Philos. Mag. A 49, 309 (1984)]. The extremely slow diffusion of Sb up to the melting temperature of GaSb is proposed to be a consequence of amphoteric transformations between native point defects which suppress the formation of those native defects which control Sb diffusion. Preliminary experiments exploring the effect of Zn indiffusion at 550 °C on Ga and Sb diffusion reveal an enhanced intermixing of the Ga isotope layers compared to undoped GaSb. However, under the same conditions the diffusion of Sb was not significantly affected.H.B. acknowledges a Feodor Lynen fellowship of the Alexander von Humboldt-Stiftung. The authors are indebted to W. Walukiewicz for valuable discussions. This work was supported in part by the Director, Office of Energy Research, Office of Basic Energy Sciences, Materials Sciences Division of the U.S. Department of Energy under Contract No.\ud DE-AC03-76SF00098, by U.S. NSF Grant No. DMR-97 32707, by the Fond der Chemischen Industrie, and by a Max-Planck Research Award.Peer reviewe