Behaviour of current in a photographic cell with a semiconductor photodetector

The evolution of spatial periodic patterns transversal to the current flow and current-voltage characteristics of a photographic cell with semiconduct or photodetector in parallel-plane geometry are studied. The photographic s ystem with a photosensitive photodetector has been studied in a wide range of the gas pressures (21-1013 hPa), discharge gaps (10 mu m-5 mm) and condu ctivities of the photodetector. A gallium arsenide photodetector (10(7)-10( 8) Ohm cm) has been used as the semiconducting cathode. The photodetector w as irradiated on the back side with light in a particular wavelength range that tons used to control the photoconductivity of the material. The photod etector was found to stabilize the discharge in the cell. The assessment of the image formation is then based on analysis of the discharge glow, visua lized by a photograph taken through the SnO2 film. When the current is incr eased above the stable limit, breakdown or small current and glow oscillati ons begin. The filamentation was primary due to the formation of a space ch arge of positive ions in the discharge gap which changed the discharge from the Townsend to the glow type.