Method for determining material parameters of a doped semiconductor substrate, including: applying electromagnetic excitation radiation in order to produce luminescent radiation in the semiconductor substrate, the temporal profile of the excitation radiation intensity is periodically modulated, so that the rate of generation of charge carrier pairs in the substrate has a maximum and minimum during an excitation period, and at least the relative temporal profile of the rate of generation G(t) is determined by time-dependent measurement of the excitation radiation intensity, time-resolved measuring luminescent radiation intensity emanating from a measuring region, at least the relative temporal profile of the intensity of the luminescent radiation Φ(t) is measured during an excitation period, determining a material parameter of the semiconductor substrate based on G(t) and Φ(t). The effective lifetime of the substrate is determined from the time difference between the maximum of G(t) and a corresponding maximum of Φ(t).