OPTOELECTRONİCS AND ADVANCED MATERİALS – RAPID COMMUNICATIONS Vol. 6, No. 1-2, January-February 2012, p. 327 - 330 Current-voltage (I-V) characteristics of Au/InGaAs/n-GaAs Schottky barrier diodes B. KINACI a,* , S. ÇÖREKÇİ b , K. KIZILKAYA a , S. ÖZÇELİK a a Department of Physics, Faculty of Science, Gazi University, 06500, Ankara, Turkey b Department of Physics, Faculty of Science and Arts, Kırklareli University, 39160, Kırklareli, Turkey In this study, the forward and reverse bias current-voltage (I-V) characteristics of Au/InGaAs/n-GaAs Schottky barrier diodes (SBDs) have been investigated at room temperature. InGaAs epilayer was grown on (100) oriented n-GaAs substrate using V80-H solid source Molecular Beam Epitaxy (MBE) system. Atomic Force Microscope (AFM) was used in order to study the surface properties of InGaAs epilayer. The AFM measurement was performed by using an Omicron variable temperature STM/AFM instrument. The electrical parameters such as barrier height ( b), ideality factor (n), series resistance (Rs) and interface states (Nss) of Au/InGaAs/n-GaAs SBDs have been calculated by using forward and reverse bias I-V measurements. The energy distribution of interface states of the structure was obtained from the forward bias I-V measurements by taking the bias dependence of the effective barrier height ( e) into account. In addition, the values of Rs and b were determined by using Cheung’s methods and results have been compared with each other. (Received November 14, 2011; accepted February 20, 2012) Keywords: InGaAs/GaAs structure, Schottky barrier diodes, Molecular beam epitaxy, Curent-voltage characteristics 1. Introductıon III-V group semiconductors, such as Gallium Arsenide (GaAs)-based structures, are used in the research and development of optoelectronics and microelectronics devices [1-7]. There are a lot of GaAs-based structure growth techniques such as Chemical vapor deposition (CVD) [8], Metal organic chemical vapor deposition (MOCVD) [7] and MBE [9-10]. Among these techniques, MBE can be used to grow samples in a high vacuum, which is important when preparing high quality samples. In addition, the reflection high energy electron diffraction (RHEED) technique has been widely applied to the study of this system. The reconstruction and growth rate of the surface were determined by RHEED oscillations [9-10]. Recently, there are many contact studies on GaAs- based structures [1,3,4,7,11-16]. Metal-Semiconductor (MS) contacts are important research tools in the characterization of new semiconductor materials and at the same time the fabrication of these structures plays a crucial role in constructing some useful devices in technology. Schottky barrier diodes which are of the most simple of the MS contact devices have an important role in the semiconductor technology. The performance of SBDs depends on such electrical parameters as ideality factor, barrier height formation at M/S interface, series resistance and interface states. Electronic properties of SBDs are characterized by these parameters. There are recently a vast number of reports of experimental studies of these characteristics parameters in a great variety of MS contacts [15-23]. In the present work, the experimental forward and reverse I-V characteristic of Au/InGaAs/n-GaAs SBDs was investigated at room temperature. b, n, R s and N ss were extracted from forward bias I-V measurements. In addition, b and R s values were determined by using Cheung’s method [24]. It was seen that there was a good agreement between the values obtained from I-V measurements and Cheung’s method. Moreover, AFM was used in order to study the surface properties of InGaAs epilayer. 2. Experimental procedure The InGaAs epilayer was grown on (100) oriented n- GaAs substrate using V80-H solid source MBE system. Prior to growth, the substrate was cleaned using acetone, methanol and deionized water for the removing of the organic impurities. In MBE system, firstly GaAs buffer layer with 700 nm thickness was grown on n-GaAs structure to provide the lattice match between the substrate and the epilayers and prevent the migration of defects and the impurities from substrate to the as grown epilayers. The sample was completed by growth of 1000 nm thickness InGaAs epilayer. For the electrical characterization of the sample, ohmic and rectifier contacts were formed using thermal evaporation system. To form the ohmic contact AuGe/Au metals with the thicknesses of 1100/1000 Å and growth rates of 3.3/3 Å/s were deposited, respectively. After the ohmic contact processes, to form the ohmic contact the sample was annealed at 400 o C for 3 min in a nitrogen ambient atmosphere. After then, the 2 mm diameter dot shaped rectifier contact was formed by deposition of high purity Au (99.999%) metal with the thickness of 1000 Å and growth rate of 3.9 Å/s.