Thresholdlike behavior of photoluminescence (PL) in heterostructure wafers is studied. It is shown that strictly speaking there is no PL threshold, and the thresholdlike dependence of PL on the pump power results from the combination of three factors: the PL spreading along the wafer surface, the change in the radiative fraction of electron-hole recombination, and the restricted aperture of the PL detector. The first two factors were found to be dominating in the wafers studied. ©1997 American Institute of Physics.