Solid State Communications 150 (2010) 1592–1596 Contents lists available at ScienceDirect Solid State Communications journal homepage: www.elsevier.com/locate/ssc Extraction of electronic parameters of Schottky diode based on an organic Indigotindisulfonate Sodium (IS) Şakir Aydoğan a,* , Ümit İncekara b , A.R. Deniz a , Abdulmecit Türüt a a Department of Physics, Faculty of Sciences, Atatürk University, 25240 Erzurum, Turkey b Department of Biology, Faculty of Sciences, Atatürk University, 25240 Erzurum, Turkey article info Article history: Received 10 December 2009 Received in revised form 22 April 2010 Accepted 18 May 2010 by R. Phillips Available online 4 June 2010 Keywords: B. Carmine D. Schottky diode D. Series resistance D. Interface states abstract An Au/Indigotindisulfonate Sodium (IS)/n-Si/Al device was fabricated and the current–voltage measure- ments of the devices showed diode characteristics. Then the current–voltage (I –V ), capacitance–voltage (C –V ) and capacitance–frequency (C –f ) characteristics of the device were investigated at room tempera- ture. The values of various junction parameters such as ideality factor, barrier height, and series resistance were determined from the forward bias I –V characteristics, Cheung method, and Norde’s function. The ideality factor of 1.73 and barrier height of 0.83 eV were calculated using current–voltage characteris- tics. It has been seen that the IS layer increases the effective barrier height of the structure because this layer creates the physical barrier between the metal and the semiconductor. The lower values of capaci- tance at high frequencies were attributed to the excess capacitance resulting from the interface states in equilibrium with the n-Si that cannot follow the alternating current (ac) signal. © 2010 Elsevier Ltd. All rights reserved. 1. Introduction Metal/semiconductor (MS) contacts or organic/inorganic semi- conductor structures [1] are of great importance since they are present in most semiconductor devices. The past decade has witnessed tremendous advances in the development of organic conductive molecular and polymeric materials and this field con- tinues to be of great scientific and commercial interest. Further- more, recently, extensive researches have been carried out for applying semiconducting organic materials to electronic devices such as organic light emitting diodes, Schottky diodes based on or- ganic materials, organic solar cells and organic field effect transis- tors. Thus, semiconducting organic materials can be used in various condensed matter physics applications. It is well known that the interfacial properties of metal/semiconductor (MS) contacts have a dominant influence on device performance, reliability and sta- bility. There is a native thin insulating layer of oxide on the sur- face of the semiconductor in most practical MS contacts. This layer converts the MS structure into a metal/insulator/semiconductor device [2]. Besides, it can be constructed as an organic thin film be- tween metal and inorganic semiconductor intentionally. This film modifies some electrical parameters of the devices. For example, Schottky barrier heights of MS contacts can be manipulated by the * Corresponding author. Tel.: +90 442 231 4073; fax: +90 442 236 0948. E-mail address: saydogan@atauni.edu.tr (Ş. Aydoğan). insertion of a dipole layer between the semiconductor and the or- ganic film. Numerous studies of thin films of organic conductors on semiconductors have been performed in order to investigate the electronic properties of various organic materials based on Schot- tky diodes. Furthermore, so far many attempts have been made to realize a modification and the continuous control of the barrier height using an organic semiconducting layer, an insulating layer and/or a chemical passivation procedure at certain metal/inorganic semiconductor interfaces, or to determine characteristic parame- ters of organic film [3–10]. The importance of interfaces for the device performance can- not be overestimated as they determine charge injection and charge flow in the devices. The electronic parameters of the in- terface may give rise to an increased contact resistance. There- fore, it is important to understand the relationship between the chemical or structural characteristics of the organic materials and metal/semiconductor interface and thus, charge carrier transport in organic materials based on Schottky diodes. For example, the dif- ference in mobility between the top-contact and bottom-contact organic based Schottky diode was associated to the different mor- phology of the organic layer near the metallic contacts. The device characteristics are dependent upon the anisotropy of the transport properties in the organic thin film [11–13]. A thin organic layer can easily be made by low cost methods and appropriate processing allows organic thin films to be produced in large areas. The characteristics of conducting organic material/inorganic semiconductor interfaces have been considered as very important since it has been indicated that restrictions on 0038-1098/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.ssc.2010.05.043