Abstract
GaSe(Sn) crystals having negative resistance also show a negative photoconductivity effect at voltages near the threshold value in a wavelength region between 1 and 2.3 μm. This effect is ascribed to a level located in the forbidden gap 0.5 to 0.55 eV above the valence band. This level is identified as that assumed by Lampert for explaining negative resistance in insulators in which double injection occurs.