The use of bias light is common practice today in photoconductance decay (PCD) measurements to analyze semiconductor samples with injection‐level dependent recombination parameters (i.e., surface recombination velocity and/or bulk lifetime). Recently, it has been shown on theoretical grounds that the previously reported recombination parameters from light‐biased PCD experiments are not theactualproperties of the investigated sample, but so‐calleddifferentialrecombination parameters [R. Brendel, Appl. Phys. A60, 523 (1995)]. In the present article the theory relevant to light‐biased PCD measurements is discussed in detail and subsequently applied to monocrystalline silicon wafers with nitride and oxide passivated surfaces in order to verify the deviations between the differential and actual surface recombination velocities. Special emphasis is paid to the experimental fact that the injection level cannot be reduced below a minimum value due to signal‐to‐noise problems. ©1996 American Institute of Physics.