Distribution of light‐induced defect states in undoped amorphous silicon has been studied by using the modulated photoconductivity spectroscopy technique. The experimental results show that a large increase of the neutral defect states occurs, and the positively charged defect states grow particularly in the midgap energy range. The qualitative features of the measured energy distribution agree well with the theoretical prediction from the current defect formation model, although a quantitative comparison with respect to the magnitude of density‐of‐states reveals a discrepancy between theory and experiment. ©1995 American Institute of Physics.