Breakdown and range of stable discharge glow in a homogeneous dc electric field are studied at various distances d between the electrodes and different inner diameters D (5, 9, 12, 18 and 22 mm) of GaAs semiconductor cathode areas. The current–voltage characteristics of the gas discharge system have been studied in a wide range of pressure p (16–760 Torr), interelectrode distances d (10 µm–5 mm) and conductivities of the GaAs cathode. The initiation of electrical breakdown as a result of secondary electron emission from the semiconductor cathode in low gas pressure is presented in this paper. In a planar gas discharge cell with diameters much larger than an interelectrode distance, the effects of different parameters (overvoltage, electrode separation, diameter and conductivities of the GaAs cathode, gas pressure, glow current, etc) on electrical breakdown and spatial stabilization of the current have been studied. The distributed resistance of photosensitive semiconductor cathode and the impact of the ionizing component of the discharge plasma on the control of the stable operation of a planar gas discharge system at atmospheric pressure are also investigated. Through spatially uniform irradiation of the semiconductor cathode, non-stationary states which are non-homogeneous can be generated in a system. The loss of stability is primarily due to the formation of a space charge of positive ions in the discharge gap which changes the discharge from the Townsend to the glow type.

Nonlinear electrical transport processes in a semiconductor‐gas discharge structure with semi‐insulating GaAs are studied for a wide range of gas pressures, interelectrode distances and different diameters of the photocathode areas. A primary destabilization of homogeneous state observed in a planar dc‐driven structure is due to nonlinear transport properties of GaAs photocathode. GaAs samples present N‐shaped negative differential conductivity under high‐electric fields and the presence of the deep electronic levels of defects, the so‐called EL2 centers, gives rise to the N‐type‐NDC of the material, as a consequence, to low‐frequency oscillations in current when a dc voltage of a high enough magnitude is applied to a GaAs photocathode. It is important to note that we have experimentally investigated the above‐mentioned nonlinear electrical characteristics of GaAs by a new‐suggested method and our experimental findings are obviously in good agreement with estimated results reported by other independent authors. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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The memory effect in the planar semiconductor gas discharge system at different pressures (15–760 Torr) and interelectrode distances (60–445 µm) was experimentally studied. The study was performed on the basis of current–voltage characteristic (CVC) measurements with a time lag of several hours of afterglow periods. The influence of the active space charge remaining from the previous discharge on the breakdown voltage (UB) has been analysed using the CVC method for different conductivities of semiconductor GaAs photocathode. CVC showed that even a measurement taken 96 h after the first breakdown was influenced by accumulated active particles deposited from the previous discharge. Such phenomena based on metastable atoms surviving from the previous discharge and recombined on the cathode to create initial electrons in the avalanche mechanism are shown to be fully consistent with CVC data for both pre-breakdown and post-breakdown regions. However, in the post-breakdown region pronounced negative differential conductivity was observed. Such nonlinear electrical property of GaAs is attributed to the existence of deep electronic defect called EL2 in the semiconductor cathode material. On the other hand, the CVC data for subsequent dates present a correlation of memory effect and hysteresis behaviour. The explanation for such a relation is based on the influence of long lived active charges on the electronic transport mechanism of semiconductor material.

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