The spectral dependences of photoconductivity in a wide temperature range (T= 80-300 K) of layered GeS single crystals, both intentionally undoped and Nd-doped, have been experimentally investigated and analyzed. In contrast to GeS single crystals, elementary exciton-type excitation has been found in the photoconductivity spectrum of Ge1 - xNdxS single crystals (x = 0.005 and 0.01) in the temperature range of 200 < T < 350 K. Upon heating, exciton-impurity complexes are decomposed, thus resulting in the excitonic photoelectric effect. After gamma irradiation at a dose of 30 kRad, no exciton states are observed in the photoconductivity spectrum. The intensity of X-ray diffraction reflections increases by a factor of similar to 35, which can be explained by decomposition of complex atomic aggregates and formation of an ordered state in layered Ge1 - xNdxS single crystals (x = 0.005 and 0.01).
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