ISSN 1063-7826, Semiconductors, 2011, Vol. 45, No. 10, pp. 1286–1290. © Pleiades Publishing, Ltd., 2011. 1286 1. INTRODUCTION Metal-oxide-semiconductor type Schottky barrier diodes (SBDs) are of great importance since they are used for the semiconductor devices. Existance of an insulator or oxide layer between metal and semicon- ductor can have strong influence the device properties as well as interface state density (N ss ). Schottky barrier heights (SBHs), ideality factor (n), and leakage cur- rent level [1–10]. GaAs is one of the A III B V semicon- ductor compounds and its electrical properties which are superior to those of silicon. Due to GaAs has a higher saturated electron velocity and higher electron mobility, allowing devices made from if for high fre- quency and low power applications [11–14]. Since these benefits, much attention has been focused on the fabrication of GaAs based oxide devices with various insulator layers such as plasma enhanced chemical vapor deposition (PECVD) SiO 2 . Some studies [15– 19] inspected the effects of the presence of an interfa- cial oxide layer and the interface states on the behavior of SBDs, and extracted the density distribution of interface states in the semiconductor band gap from the forward-bias current–voltage (I–V) characteristics. Also, in our previous works [20, 21], we showed the effects of the interfacial insulator layer on the properties of these devices with thin SiO 2 dielectric film. In this study, thin and thick SiO 2 dielectric layers deposited on high quality n-type GaAs semiconductor substrate to explain effects of dielectric layer thickness on electrical parameters for Au/SiO 2 /n-GaAs SBDs. We calculated main electrical parameters such as, nφ Bo and R s , and N ss for Au/SiO 2 /n-GaAs SBDs obtained from I–V and capacitance–voltage (C–V) character- ictics at room temperature and compared with each other. 2. EXPERIMENTAL METHOD Au/SiO 2 /n-GaAs SBDs have been prepared using epiready n-type GaAs wafers with (100) orientations and (2–3) × 10 18 cm –3 carrier concentration. For the fabrication process, GaAs wafers were dipped in Ammonium Peroxide for a few seconds to remove native oxide layer on the surface. Au/Ge/Ni ohmic contacts were thermally evaporated to back of the wafers and annealed at 430°C for 40 s. Thin (60 Å) and thick (250 Å) SiO 2 dielectric layers was coated by PECVD technique. SiH 4 gas was used for Si source and O 2 gas used for oxygen source. SBDs with thin and thick SiO 2 insulator layers were named sample 1 and sample 2, respectively. AFM images of 4 μm 2 scan area were recorded using the needle mode operation on an Omicron VT-STM/AFM system. The root mean square (rms) roughness values were processed from the surface topographies of the samples by Scala Pro soft- ware. Circular Au Schottky contacts with 1mm diam- eters and 1500 Å thickness were evaporated on both samples in the vacuum system. SEMICONDUCTOR STRUCTURES, LOW-DIMENSIONAL SYSTEMS, AND QUANTUM PHENOMENA Electrical Characteristics of Au/n-GaAs Structures with Thin and Thick SiO 2 Dielectric Layer 1 H. Altuntas a , S. Altindal b , S. Corekci c , M. K. Ozturk b , and S. Ozcelik b a Department of Physics, Faculty of Sciences, Çankiri Karatekin University, 18100 Çankiri, Turkey e-mail: altunhalit@gmail.edu.tr b Department of Physics, Faculty of Arts and Sciences, Gazi University, 06500 Ankara, Turkey c Department of Physics, Faculty of Arts and Sciences, Kirklareli University, 3900 Ankara, Turkey Received February 1, 2011; in final form, March 27, 2011 Abstract—The aim of this study, to explain effects of the SiO 2 insulator layer thickness on the electrical prop- erties of Au/n-GaAs Shottky barrier diodes (SBDs). Thin (60 Å) and thick (250 Å) SiO 2 insulator layers were deposited on n-type GaAs substrates using the plasma enganced chemical vapour deposition technique. The current–voltage (I–V) and capacitance–voltage (C–V) characteristics have been carried out at room tem- perature. The main electrical parameters, such as ideality factor (n), zero-bias barrier height (φ Bo ), series resistance (R s ), leakage current, and interface states (N ss ) for Au/SiO 2 /n-GaAs SBDs have been investigated. Surface morphologies of the SiO 2 dielectric layer was analyzed using atomic force microscopy. The results show that SiO 2 insulator layer thickness very affects the main electrical parameters. Au/n-GaAs SBDs with thick SiO 2 insulator layer have low leakage current level, small ideality factor, and low interface states. Thus, Au/n-GaAs SBDs with thick SiO 2 insulator layer shows better diode characteristics than other. DOI: 10.1134/S1063782611100034 1 The article is published in the original.