Influence of doping density on electronic transport in degenerate Si:Pδ-doped layers

Abstract

We present a detailed study addressing the effect of doping density on electronic transport in Si:P $\ensuremath{\delta}$-doped layers grown by phosphine dosing and low temperature molecular beam epitaxy. We demonstrate that the surface P coverage can be determined directly from scanning tunneling microscope analysis of $\mathrm{P}{\mathrm{H}}_{3}$ dosed Si(100) surfaces, with good quantitative agreement to that measured by Auger electron spectroscopy. For samples with doping densities between $\ensuremath{\sim}1\ifmmode\times\else\texttimes\fi{}{10}^{13}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}\ensuremath{\sim}5\ifmmode\times\else\texttimes\fi{}{10}^{14}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}$, we found that mobility decreases with higher doping. In contrast, both the mean free path and phase coherence length increase with doping density up to a maximum at a room-temperature saturation dose of phosphine $(\ensuremath{\sim}2\ifmmode\times\else\texttimes\fi{}{10}^{14}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2})$. We discuss the implications of our results for the fabrication of nanoscale Si:P devices by scanning probe lithography and phosphine dosing.