This article reports the effect of n-type GaAs substrate orientation, namely (100),
IntroductionEssentially conducting polymers, such as polyaniline (PANI), sulfonated polyaniline (SPAN), poly(p-phenylene-vinylene), polypyrrole, polyacetylene, polythiophene, etc., are promising semiconductors materials with confirmed technological potential due to their unique optical and electrical properties [1]. Among the family of organic semiconductors, the semiconducting polymers have attracted the most attention for applications in electronic and optoelectronic devices, particularly due to their exceptional electrical properties and easy synthesis [2][3][4]. As a result, this category of polymers has been used in several applications such as organic light emitting diodes (OLEDs) [5,6], solar cells [7,8] As it is well known, the crystallographic orientation of the substrate has a significant effect on incorporation of impurities and defects and consequently on optical and electronic properties of III-V materials [28]. The ideality factor n and barrier height (BH) as well as the electrical characteristics are fundamental parameters of a Schottky barrier diode (SBD) and these give an indication about the quality of the Schottky interface. The SBD parameters must be determined over a broad range of temperatures because the analysis of the current-voltage (I-V) characteristics of the SBD measured only at room temperature does not provide accurate information about the conduction mechanism and the barrier nature created at metal semiconductor interface in order to understand these phenomena and determine precisely the parameters of the Schottky diodes. Chand et al. [29] and Hardikar et al.[30] analysed the experimental currentvoltage data which revealed that there is an increase in the ideality factor and a decrease in the zero-bias barrier height with decreasing temperature. Consequently, the ideality factor and the barrier height established from forward I-V characteristics are found to be temperature dependent. This confirms that the Schottky barrier height is inhomogeneous in nature at the interface. This behaviour has been successfully described on the basis of the thermionic emission mechanism with Gaussian distribution of the barrier heightTo fabricate a hybrid organic/inorganic semiconductor heterojunction device with the aim to obtain specific optical and electrical properties on the bases of their doping levels, a thin organic film is deposited onto the surface of a conventional inorganic semiconductor substrate. This can be done by simple and inexpensive methods such as 4 spin coating used for thin film deposition at room temperature. Recently, a new technique of SPAN films preparation has been developed by Yang et al. [32].In this paper, we report on the fabrication and electrical characterization of Au/SPAN/GaAs heterojunctions grown on three different substrate orientations, namely n-type GaAs (100), (311)A and (311)B. We have investigated the effect of the substrate orientation on the heterojunction parameters ...