Limits on the magnitude of bandgap narrowing and Auger recombination in heavily phosphorus-diffused silicon layers ∼ 1020cm-3have been measured by electron-beam-induced current. It is determined that the slope of the bandgap narrowing versus doping must be nearly zero above 3 × 1019cm-3to be consistent with previous data at lower doping levels. It is also shown that the low-level minority-carrier lifetime in these layers is consistent only with an Auger recombination coefficient C_{N} cm6/s.