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The physical processes determining the functions of an ionization system and especially the discharge stabilization by the distributed resistance of a semiconducting cathode in such a system are studied. The current - voltage (I - U) characteristics of the system with a semiconducting GaAs cathode are obtained experimentally as functions of the gap pressure P (16 - 760 Torr) and inter-electrode distance d ( to 5 mm), which are varied for the first time over very wide ranges. The experiments showed that the presence of the distributed resistance affects the passage of the discharge current so that the discharge glows uniformly throughout the cathode surface and is not divided into separate filaments. The loss of stability was primarily due to the formation of a space charge of positive ions in the discharge gap which changed the discharge from the Townsend to the glow type.

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Gas breakdown in air in a planar gas discharge system was studied experimentally at various distances L between the electrodes and different diameters R of the electrode areas of the semiconductor cathodes. The cathode was irradiated on the back-side with light in a particular wavelength range that was used to control the photoconductivity of the material. The current-voltage characteristics of the gas discharge system with a large-diameter GaAs semiconductor cathode were studied in a wide range of the gas pressure p (28-550 Torr), interelectrode distances L (45-330 µm), and conductivities of the cathode. We show that for all experimental conditions the current density increases over the entire range of voltages U > U dc as the diameters R of the electrode areas increase. It is shown that, for arbitrary geometric dimensions of the semiconductor cathode (in the range of L/R under investigation), the ratio of the breakdown electric field to the gas pressure holds constant (E dc /p) min ≈ const. at the breakdown curve minimum. The breakdown voltage U dc is a function of both the product of the gas pressure p by the distance L and the ratio L/R (U dc = f (pL, L/R).

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