The effect of annealing temperature on the electrical characterization of Co/n type GaP Schottky diode _ I. Orak a, *, K. Ejderha b , E. Sönmez c , M. Alanyalıo  glu d , A. Turut e a Vocational School of Health Services, Bingöl University, 12000 Bingöl, Turkey b Vocational School of Technical Sciences, Bingöl University, 12000 Bingöl, Turkey c Department of Physics, Kazim Karabekir Education Faculty, Atatürk University, Erzurum 25240, Turkey d Faculty of Science, Department of Chemistry, 25240 Erzurum, Turkey e Faculty of Sciences, Department of Engineering Physics, Istanbul Medeniyet University, 34730 Istanbul, Turkey A R T I C L E I N F O Article history: Received 18 February 2014 Received in revised form 7 September 2014 Accepted 28 October 2014 Available online 29 October 2014 Keywords: Effect of thermal annealing DC magnetron sputtering Surface morphology Schottky diode GaP Ideality factor A B S T R A C T The Co/n-GaP nano-Schottky diodes have been fabricated to investigate effect of annealing temperature on the characteristics of the device. DC Magnetron sputtering technique has been used for Co metallic contact. The samples have been annealed for three minutes at 400  C and 600  C. XRD analyzes of the devices subjected to thermal annealing process have been investigated. Surface images have been taken with atomic force microscopy (AFM) in order to examine the morphology of the surface of the metal layer before and after the annealing the sample. The current–voltage (I–V) measurements taken at room temperature have shown that the ideality factor and series resistance decrease with the increasing annealing temperature. The ideality factor was found to be 1.02 for sample annealed at 400  C. Before and after annealing, depending on the temperature measurement, the capacitance–frequency (C–f), and conductance–frequency (G–f) have been measured, and graphs have been plotted. ã 2014 Elsevier Ltd. All rights reserved. 1. Introduction Metal/semiconductor (MS) contacts structures are basic devices in technology [1] and the most commonly used rectifying contacts play an important role in the electronic and optoelectronic industry [2–5]. Especially, gallium phosphide (GaP) surface has been less studied than GaAs or InP surfaces as III–IV compounds [6]. GaP is an amazing III–V semiconductor which has potential high-temperature applications because of its rather wide band gap (2.25 eV) [7,8]. Therefore, GaP used to fabricated photodiodes, in visible light emission diodes (LEDs) and field effect transistor (FET) [5–8]. Ismail et al. [6] have discussed experimental results relevant to (111) and (110) chemically etched GaP surfaces. They used to determine the surface composition resulting from etching with several solutions to determine by Auger electron spectroscopy. They [6] have compared the current–voltage (I–V), capacitance– voltage (C–V) of Au/n-GaP, and In/n-GaP Schottky diodes, and concluded that the diode characteristics depend on the surface contamination such as residual oxide and metal. Duman et al. [8] have fabricated Ni/n-GaP Schottky diodes by DC magnetron deposition. They [8] have measured the I–V and C–V and capacitance–frequency (C–f) characteristics of Ni/n-GaP Schottky contacts in the temperature range of 120–320 K by steps of 20 K and have calculated some diode parameters such as ideality factor (n) and barrier height (F b ) and series resistance (R s ). Mientus et al. [9] have fabricated Ag/GaP Schottky diode by Radio-frequency magnetron sputtering technique. They are realized GaP Schottky barrier photodiode under a highly UV. They concluded that the device exhibits well electrical characterizations. Tan et al. [10] have investigated electrical characterization and photovoltaic effect of Metal/n-GaP Schottky barrier diodes. They have used some metals such as Pt, Au, Ni, Mo, Al, Cr, Ag, and Cu. They have calculated ideality factor (n) and barrier height (F). The diodes parameters have compared with those in the literature. The purpose of this work is to explain Schottky diode and effect of thermal annealing temperature on electrical characteristics of the Co/n-GaP. 2. Experimental details In the study, Co/n-GaP nano-Schottky diodes were fabricated using n-type GaP semiconductor that were grown in the direction of (2 2 2), had the thickness of 400 mm and carrier density of * Corresponding author. Tel.: +90 4262160012; fax: +90 4262150877. E-mail addresses: ikramorak@gmail.com, iorak@bingol.edu.tr ( _ I. Orak). http://dx.doi.org/10.1016/j.materresbull.2014.10.066 0025-5408/ ã 2014 Elsevier Ltd. All rights reserved. Materials Research Bulletin 61 (2014) 463–468 Contents lists available at ScienceDirect Materials Research Bulletin journal homepage: www.else vie r.com/locat e/mat resbu