Inhomogeneities in 130 MeV Au 12+ ion irradiated Au/n-Si (1 0 0) Schottky structure Sandeep Kumar a, * , Y.S. Katharria a , V. Baranwal b , Y. Batra a , D. Kanjilal a a Inter-University Accelerator Centre, P.O. Box 10502, New Delhi 110067, India b Department of Physics, University of Allahabad, Allahabad 211002, India Received 18 July 2007; received in revised form 4 November 2007; accepted 5 November 2007 Available online 17 November 2007 Abstract The electrical characteristics of Au/n-Si (1 0 0) Schottky rectifier have been studied in a wide irradiation fluence range using conventional current–voltage (I–V) and capacitance–voltage (C–V) measurements. The I–V characteristics showed an abnormal increase in forward current at low voltage. The device shows a bend in forward I–V and reverses bias C–V characteristics due to extra current, suggesting that there are two independent contributions to thermionic current, corresponding to two levels of the Schottky barrier. It is shown that the excess current at low voltage can be explained by taking into account the role of heavy ion irradiation induced defects at the metal semiconductor interface. # 2007 Elsevier B.V. All rights reserved. PACS : 61.80.Jh; 73.30.+y; 73.40.c; 73.40.QV Keywords: Ion irradiation; Schottky barrier; I–V characteristics 1. Introduction The increasing interest of the heavy ion beams in processing technologies motivates us carrying out studies on effect of heavy ion irradiation on semiconductors [1–3]. Metal– semiconductor (MS) structure based devices have been of considerable interest due to their widespread application in terahertz meta material devices, microwave FETs, RF detectors and solar cells [4]. Formation and modification of potential barrier in a metal semiconductor interface is an exciting field of research. The position of the Fermi level within the semiconductor band-gap determines the height of this potential barrier. In general the exact position of the Fermi level depends on the properties of the interface and the electrical characteristics of Schottky contacts are very sensitive to the properties of the MS interface. As an interface is not atomically flat, so it is reasonable to assume that interface properties like atomic orientation and interface state density vary spatially. Consequently, the coexistence of different barrier heights may take place. The origins of electrical noise in Schottky diodes have been investigated in terms of barrier height inhomogeneity [5]. The inhomogeneity was suggested from the difference between the barrier heights evaluated by I–V measurements and that evaluated by C–V measurements. Ion irradiation is a well-established technique used to modify electrical, mechanical and other physical properties of materials in defined regions. While the ion implantation has been already used in the past to tailor the Schottky barrier heights (SBH) in silicon [6–9], the modification of Schottky barrier heights on Si induced by swift heavy ion (SHI) irradiation was not investigated extensively till now. The irradiation work on silicon is very important for understanding the behavior of Si devices, which are used in radiation environments like space, nuclear reactors and particle detectors [10–12]. Moreover, the SHI irradiation is useful in some applications like controlled reduction of the minority carrier lifetime in silicon power devices [13], formation of deep buried layers [14], and introduction of controlled amount of defects in semiconductors [15]. The modifications induced by SHI irradiation in the MS interface property of Schottky diode can be investigated systematically by studying their electrical behavior. www.elsevier.com/locate/apsusc Available online at www.sciencedirect.com Applied Surface Science 254 (2008) 3277–3281 * Corresponding author. Tel.: +91 11 26893955; fax: +91 11 26893666. E-mail address: sandeepiuac@gmail.com (S. Kumar). 0169-4332/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2007.11.014