Diffusion and Charge Dynamics of Negatively Charged Muonium in<i>n</i>-Type GaAs

Abstract

We report measurements on the dynamics of negatively charged muonium ( ${\mathrm{Mu}}^{\ensuremath{-}}$) from 295 to 1000 K in heavily doped n-type GaAs:Si. The ${\mathrm{Mu}}^{\ensuremath{-}}$ center begins to diffuse above $500\mathrm{K}$ with a hop rate described by an Arrhenius function $\ensuremath{\nu}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}{\ensuremath{\nu}}_{0}{e}^{{\ensuremath{-}E}_{\ensuremath{\mu}}/{k}_{B}T}$ where ${\ensuremath{\nu}}_{0}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}5.6(5)\ifmmode\times\else\texttimes\fi{}{10}^{12}\phantom{\rule{0ex}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$ and ${E}_{\ensuremath{\mu}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.73(1)\phantom{\rule{0ex}{0ex}}\mathrm{eV}$. Above $700\mathrm{K}$, relaxation from charge-state fluctuations is observed. The analysis of these data implies ${\mathrm{Mu}}^{\ensuremath{-}}\ensuremath{\leftrightarrow}{\mathrm{Mu}}^{0}$ conversions occur via alternating capture of holes and electrons, establishing Mu as a deep recombination center. Similar dynamics are expected for the isolated ${\mathrm{H}}^{\ensuremath{-}}$ center in n-type GaAs.