A demonstration of donor passivation through direct formation of V-As i complexes in As-doped Ge1− x Sn x

Abstract

Positron annihilation spectroscopy in the Doppler and coincidence Doppler mode was applied on Ge1−xSnx epitaxial layers, grown by chemical vapor deposition with different total As concentrations (∼1019–1021 cm−3), high active As concentrations (∼1019 cm−3), and similar Sn concentrations (5.9%–6.4%). Positron traps are identified as mono-vacancy complexes. Vacancy-As complexes, V-Asi, formed during the growth were studied to deepen the understanding of the electrical passivation of the Ge1−xSnx:As epilayers. Larger mono-vacancy complexes, V-Asi (i≥2), are formed as the As doping increases. The total As concentration shows a significant impact on the saturation of the number of As atoms (i=4) around the vacancies in the sample epilayers. The presence of V-Asi complexes decreases the dopant activation in the Ge1−xSnx:As epilayers. Furthermore, the presence of Sn failed to hinder the formation of larger V-Asi complexes and thus failed to reduce the donor-deactivation.