Nonlinear electrical transport of semi-insulating (SI) GaAs detector in semiconductor-gas discharge IR image converter (SGDIC) are studied experimentally for a wide range of the gas pressures (p - 28-55 Torr), interelectrocle distances (d = 445-525 mu m) and inner electrode diameters (D = 12-22 mm) of photocathode. The destabilization of homogeneous state observed in a planar dc-driven structure is due to nonlinear transport properties of GaAs photocathode. Experimental investigation of electrical instability in SGDIC structure was analyzed using hysteresis, N-shaped negative differential conductivity (NDC) current voltage characteristics (CVC) and dynamic behavior of current in a wide range of feeding voltage (U = 590-1000 V) under different IR light intensities incident on cathode material. It is established that hysteresis are related to electron capture and emission from EL2 deep center on the detector substrate. We have experimentally investigated domain velocity and electron mobility based on well-understood transferred electron effect (TEE) for abovementioned nonlinear electrical characteristics of Sl GaAs. The experimental findings are in good agreement with estimated results reported by other independent authors. (C) 2009 Elsevier Ltd. All rights reserved.