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M. Elsayed, R. Krause-Rehberg, B. Korff, S. Richter, H. S. Leipner
Identification of As-vacancy complexes in Zn-diffused GaAs.
J. Appl. Phys. 113, 9 (2013), 094902

We have used positron annihilation spectroscopy to study the introduction of point defects in Zn-diffused semi-insulating GaAs. The diffusion was performed by annealing the samples for 2?h at 950?°C. The samples were etched in steps of 7??m. Both Doppler broadening using slow positron beam and lifetime spectroscopy studies were performed after each etching step. Both techniques showed the existence of vacancy-type defects in a layer of about 45??m. Secondary ion mass spectroscopy measurements illustrated the presence of Zn at high level in the sample almost up to the same depth. Vacancy-like defects as well as shallow positron traps were observed by lifetime measurements. We distinguish two kinds of defects: As vacancy belongs to defect complex, bound to most likely one Zn atom incorporated on Ga sublattice, and negative-ion-type positron traps. Zn acceptors explained the observation of shallow traps. The effect of Zn was evidenced by probing GaAs samples annealed under similar conditions but without Zn treatment. A defect-free bulk lifetime value is detected in this sample. Moreover, our positron annihilation spectroscopy measurements demonstrate that Zn diffusion in GaAs system is governed by kick-out mechanism.

Keywords: arsenic, complex, vacancies, diffusion, gallium arsenide, positron annihilation, lifetime, annealing, etch, beam, SIMS

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