Kinetics of divacancy annealing and divacancy-oxygen formation in oxygen-enriched high-purity silicon

Abstract

In this work the thermal kinetics of the transformation from the divacancy $({\mathrm{V}}_{2})$ to the divacancy-oxygen $({\mathrm{V}}_{2}\mathrm{O})$ complex has been studied in detail, and activation energies, $({E}_{a})$, have been obtained. Diffusion oxygenated float-zone silicon (DOFZ-Si) samples of $n$-type with a doping of $5\ifmmode\times\else\texttimes\fi{}{10}^{12}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ and oxygen content of $(2--3)\ifmmode\times\else\texttimes\fi{}{10}^{17}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ have been irradiated with $15\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$ electrons. Isothermal annealing studies of electrically active defects have been performed by means of deep-level transient spectroscopy. Heat treatments at temperatures in the range $205\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}--285\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ have all shown a shift in the singly negative and doubly negative divacancy levels, due to the annealing of ${\mathrm{V}}_{2}$ and the formation of ${\mathrm{V}}_{2}\mathrm{O}$. By studying the temperature-dependent rate of this process which exhibits first order kinetics, it has been found that both the annealing ${\mathrm{V}}_{2}$ and the formation of ${\mathrm{V}}_{2}\mathrm{O}$ have activation energies of $\ensuremath{\approx}1.3\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. This value is ascribed to migration of ${\mathrm{V}}_{2}$, and the results favor strongly a model where ${\mathrm{V}}_{2}$ is trapped by interstitial oxygen atoms during migration. In addition, the process takes place with a high efficiency since the loss of ${\mathrm{V}}_{2}$ and the growth of ${\mathrm{V}}_{2}\mathrm{O}$ display a close one-to-one proportionality. Finally, it has been found that the diffusivity pre-exponential factor, ${D}_{{\mathrm{V}}_{2}}^{0}$, for ${\mathrm{V}}_{2}$ is in the range $3\ifmmode\pm\else\textpm\fi{}1.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{2}∕\mathrm{s}$, which agrees well with a simple theoretical model of ${\mathrm{V}}_{2}$ diffusion in Si.