Electron-hole droplets and impurity band states in heavily doped Si(P): Photoluminescence experiments and theory

Abstract

The photoluminescence spectrum of phosphorus-doped silicon at dopant concentrations ranging from 1.2 \ifmmode\times\else\texttimes\fi{} ${10}^{17}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ to 4 \ifmmode\times\else\texttimes\fi{} ${10}^{19}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ is studied as a function of excitation power. The results are interpreted in terms of recombination of charge carriers inside an electron-hole drop and of a free hole with an electron loosely bound to an impurity site. Comparison is made with theoretical estimates of the impurity band density of states outside the drop and improved estimates of the charge carrier density and threshold energy associated with the electron-hole liquid.