[en] The electronic and optical properties of a-Si,Ge:H,F alloys are investigated for the initial (as-grown) state as well as after annealing, light soaking, and subsequent annealing. The optical absorption spectra were determined from optical transmission, the constant photocurrent technique and photothermal deflection spectroscopy. The photoconductivity and the temperature dependence of the dark conductivity were measured. A post-deposition anneal was found to improve the measured properties for some of the alloys. The properties of the high gap, E/sub opt/ > 1.4 eV, and the low gap, E/sub opt/ < 1.4 eV, alloys change differently with light soaking. For the high gap alloys, there is an increase in the subgap absorption, a decrease in the photoconductivity and the dark conductivity and an increase in the activation energy with light exposure. The gap alloys show increasing subgap absorption with light soaking, however, the photoconductivity remains constant and the dark conductivity increases and its activation energy decreases