Analysis of temperature dependent electrical characteristics of Au/n-GaAs/GaAs structures in a wide temperature range A. Bengi a, * , S. Altındal a , S. O ¨ zçelik a , S.T. Agaliyeva b , T.S. Mammadov a, b a Physics Department, Faculty of Arts and Sciences, Gazi University, 06500 Ankara, Turkey b National Academy of Science, Institute of Physics, Baku, Azerbaijan article info Article history: Received 12 February 2008 Accepted 8 July 2008 Keywords: Au/n-GaAs/GaAs structures I–V–T measurements C–V–T measurements Current conduction mechanisms Multistep tunneling PACS: 73.30.þy 73.40.-c 73.40.Ei 73.40.Qv abstract The temperature dependence of some electrical parameters of Au/n-GaAs/GaAs structures obtained from the forward bias current–voltage (I–V) and reverse bias capacitance–voltage (C–V) characteristics is studied in the temperature range of 79–400 K. The forward bias current I is found to be proportional to I o (T)exp(AV), where A is the slope of Ln(I)–V curves and almost independent of the voltage and temperature, and I o (T) is relatively a weak function of temperature. The semi-logarithmic Ln(I)–V char- acteristics based on the thermionic emission (TE) mechanism showed a decrease in the ideality factor (n) and an increase in the zero-bias barrier height (F Bo ) with increasing temperature. These behaviors don’t obey the pure thermionic emission (TE) theory. However, the barrier height F B (C–V) determined from the C 2 –V plot at high frequency decreased linearly with the temperature. Analysis of the data indicated that the predominant current conduction mechanism of our sample was a trap-assisted multistep tunneling rather than the other mechanisms. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction In general, the forward bias current–voltage (I–V) characteristics of metal–semiconductor (MS) or metal–insulator–semiconductor (MIS) contacts are linear on a semi-logarithmic scale at interme- diate forward bias voltage, but deviate considerably from linearity at low temperatures and high voltages due to the effect of series resistance (R s ) and the density of surface states (N ss ). The presence of the interfacial insulator layer d (such as SiO 2 ), series resistance R s and density of surface states N ss strongly influences the electrical characteristics of these types of devices. However, the role of other effects gives increase to the observed deviations in the I–V char- acteristics of real devices, such as front/back contacts to the diode, carrier tunneling through barrier, surface effects, and inherent bulk condition in the semiconductor material and doping levels. Due to the technological importance of such devices, there have been made a great number of studies in the last few decades [1–19]. The popularity of these studies, which is rooted in their importance to the semiconductor industry, does not assure uniformity of the results or of interpretation. There are a great number of carrier conduction mechanisms such as thermionic emission (TE), thermionic field emission (TFE), field emission (FE), minority carrier injection, recombination-generation and multistep tunneling which compete and usually one of them may dominate over the others in certain temperature and voltage region [16,17]. However, simultaneous contribution from two or more mechanisms could also be possible. There are several reasons, which cause the device to deviate from the ideal behavior and must be taken into account. These include the effects of interfacial insulator layer, interface states and carrier transport mechanisms. In order to find whether the fabricated Schottky diode (SD) is ideal or not, the forward bias I–V and reverse bias C–V characteristics in a wide temperature range are considered. Horvarth [4], independent from Card and Rhoderick [3], derived an expression for the ideality factor n, giving the contribution of the interfacial insulator layer and the density of surface states to the Schottky barriers’ lowering, and evaluated the interface state energy distribution and the relative interfacial insu- lator layer thickness. The presence of interfacial insulator layer d leads to an increase in the ideality factor value n. This increase can be explained in terms of surface states which do not equilibrate with the metal and also with the potential drop across the insulator layer [3]. * Corresponding author. Tel.: þ90 312 212 6030/1247; fax: þ90 312 212 2279. E-mail address: aylinbengi@gmail.com (A. Bengi). Contents lists available at ScienceDirect Vacuum journal homepage: www.elsevier.com/locate/vacuum 0042-207X/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.vacuum.2008.07.003 Vacuum 83 (2009) 276–281