Divacancy complexes induced by Cu diffusion in Zn-doped GaAs

• Published in: The European physical journal. B, Condensed matter physics Vol. 86; no. 8
• Main Authors: Elsayed, M., Krause-Rehberg, R., Korff, B., Ratschinski, I., Leipner, H. S.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.08.2013; EDP Sciences
• Subjects: Complex Systems; Condensed Matter Physics; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Defects and impurities in crystals; microstructure; Diffusion in solids; Diffusion of impurities; Exact sciences and technology; Fluid- and Aerodynamics; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Other interactions of matter with particles and radiation; Physics; Physics and Astronomy; Point defects (vacancies, interstitials, color centers, etc.) and defect clusters; Positron annihilation; Regular Article; Solid State Physics; Structure of solids and liquids; crystallography; Transport properties of condensed matter (nonelectronic); Solid State and Materials; Complex defect; Doppler broadening; Gallium arsenides; Annealing; Acceptor center; Zinc additions; Divacancy; Impurity diffusion; Vacancy cluster; Positron annihilation; Activation energy; Defect formation
• ISSN: 1434-6028; 1434-6036
• DOI: 10.1140/epjb/e2013-40414-7

Positron annihilation spectroscopy was applied to investigate the nature and thermal behavior of defects induced by Cu diffusion in Zn-doped p -type GaAs crystals. Cu atoms were intentionally introduced in the GaAs lattice through thermally activated diffusion from a thin Cu capping layer at 1100 °C under defined arsenic vapor pressure. During isochronal annealing of the obtained Cu-diffused GaAs in the temperature range of 450−850 K, vacancy clusters were found to form, grow and finally disappear. We found that annealing at 650 K triggers the formation of divacancies, whereas further increasing in the annealing temperature up to 750 K leads to the formation of divacancy-copper complexes. The observations suggest that the formation of these vacancy-like defects in GaAs is related to the out-diffusion of Cu. Two kinds of acceptors are detected with a concentration of about 10 16 − 10 17 cm −3 , negative ions and arsenic vacancy copper complexes. Transmission electron microscopy showed the presence of voids and Cu precipitates which are not observed by positron measurements. The positron binding energy to shallow traps is estimated using the positron trapping model. Coincidence Doppler broadening spectroscopy showed the presence of Cu in the immediate vicinity of the detected vacancies. Theoretical calculations suggested that the detected defect is V Ga V As -2Cu Ga .