Surface recombination velocity of highly doped n-type silicon

New experimental data for the minority-carrier surface recombination velocity of n-type silicon, Sp, are reported. The data, obtained from photoconductance decay measurements of the recombination currents corresponding to different phosphorus diffusions, include oxide-passivated, unpassivated and metal-coated surfaces. For the passivated case, Sp increases linearly with surface dopant density, ND, for dopant densities higher than 1×1018 cm−3, while for unpassivated (bare) and for metal-coated silicon Sp remains essentially constant, at about 2×105 cm/s and 3×106 cm/s, respectively. The experiments also allow for a determination of the apparent energy bandgap narrowing as a function of dopant density, ΔEgapp=14 meV [ln(ND/1.4×1017 cm−3)]. These surface recombination velocity and ΔEgapp data form, together with the dependences of minority-carrier lifetime, τp, and mobility, μp, used in the analysis, a consistent set of parameters that fully characterize highly doped n-type silicon.