Boron acceptor concentration in diamond from excitonic recombination intensities

Abstract

Excitonic recombinations are investigated by cathodoluminescence in a series of homoepitaxial diamond layers doped with boron in the range $(2\ifmmode\times\else\texttimes\fi{}{10}^{16})$--$(5\ifmmode\times\else\texttimes\fi{}{10}^{18}) \mathrm{at} {\mathrm{cm}}^{\ensuremath{-}3}.$ As opposed to earlier observations made on polycrystalline boron-doped diamond, we show that the ratio between the neutral-boron bound exciton and the free-exciton recombination intensities is proportional to the boron content up to $6\ifmmode\times\else\texttimes\fi{}{10}^{17}$cm${}^{\ensuremath{-}3}$ and starts to saturate above this value. The probability of an exciton in diamond being trapped by only one boron impurity is calculated and appears to be in good agreement with the observed saturation, suggesting the formation of excitons bound to near-neighbor boron pairs at high boron concentrations.