The paper reports results of study of photoconductivity spectrum of sulfur- doped samples of silicon (initial p-type silicon with r = 1 Ohm×cm) under dark conditions and while samples were subjected to constant light in forward and reverse switching modes. The authors report negative photoconductivity of the diode structure in forward mode, which is most likely associated with the injection of current carriers, associated with the level E = 0,4 eV. A sharp decrease in photoconductivity was detected at E »0,52 eV, where one can witness infrared quenching of photoconductivity (IRQ) in samples in forward and reverse modes in light