Electrical Characteristics of Pd/ZnO Nanowires (NWs)-based Schottky Diodes Grown on Zn Seed Layercoated n-Si Substrates Divya Somvanshi Department of Electronics Engineering Indian Institute of Technology (BHU), Varanasi Uttar Pradesh-221005, India dsomvanshi.rs.ece@iitbhu.ac.in Satyabrata Jit Department of Electronics Engineering Indian Institute of Technology (BHU), Varanasi Uttar Pradesh-221005, India sjit.ece@iitbhu.ac.in Abstract—Pd/ZnO Nanowires (NWs)-based Schottky diodes have been fabricated on Zn seed layer-coated n-Si substrates by a simple thermal evaporation method. The surface morphology and crystalline structure of ZnO NWs have been investigated by FESEM and XRD. The Pd/ZnO NWs Schottky diodes exhibit a typical non-linear rectifying behavior with excellent rectification ratio (I F /I R ) ~ 7561 at ± 2 V, barrier height eff B, φ ~ 0.78 eV and ideality factor η ~ 2.10 at room temperature. The value of series resistance has been calculated from the forward bias I-V characteristics using Cheung’s method and Norde method. Index Terms—Nanowires, Schottky barrier diode, seed layer. I. INTRODUCTION Among various metal oxide nanostructures, the nanostructures of ZnO (II–VI semiconductor) possess a special place in semiconductor R&D due to its tremendous properties and applications [1, 2]. ZnO is a well-known wide band gap (3.37 eV) semiconductor material with exciton binding energy of 60 meV. It exhibits typical n-type conductivity due to presence of different native defects such as zinc interstitials, oxygen vacancies, and zinc vacancies in the crystal lattice [1- 3]. Nanostructures of ZnO such as nanowires nanorods, nanobelts, nanorings etc [1, 2] possess a promising future owing to the variety of optical and electrical properties which are technologically useful for various electronic, optoelectronic and gas sensing applications [1-3]. Among them, ZnO nanowires (NWs) are prime candidates for various electronic and optoelectronic applications due to their excellent optical, electrical, and piezoelectric properties [2, 4]. Schottky contacts are the basic building block of a number of semiconductor electronic devices, such as field effect transistors (FETs), nanogenerator, solar cells and photo detectors, etc. [1, 2, 5]. Due to the technological importance of Schottky diodes, a clear understanding of their electrical characteristics is of great interest. Typically, the forward bias current–voltage (I–V) characteristics are linear in the semi- logarithmic scale at low voltages; however, they deviate considerably from linearity due to effects of parameters such as the series resistance, interfacial oxide layer and interface states at sufficiently large applied voltage [5-8]. Good quality rectifying Schottky contacts with high barrier height, low ideality factor and series resistance on the n-ZnO thin film surface are crucial for many electronic and optoelectronic applications [5, 9]. The presence of surface states such as native defects and adsorbents [14] on ZnO thin film surfaces can easily result in the pinning of the Fermi level in the middle of the band gap thereby decreasing the Schottky barrier height (SBH) of the rectifying contacts [4, 7, 9]. With this in view, different surface treatment methods such as the O 2 plasma treatment [10], chemical treatments [5] and H 2 O 2 treatment [11] etc., have been used by various researchers [5, 10, 11] for modifying the surface of the ZnO films. However, their use could be highly undesirable, since these methods are complicated and may easily damage the ZnO surface. Therefore, in the present work we have deposited a large- area Pd Schottky contact on ZnO thin films fabricated on Zn seed layer n-Si substrates by the thermal evaporation method. Further, electrical parameters such as barrier height, ideality factor and series resistance have been extracted from current- voltage characteristics, Cheung’s method and Norde method. II. EXPERIMENTAL DETAILS The fabrication process of Pd/ZnO thin film Schottky diodes grown on Zn seed layer coated n-Si substrates were reported elsewhere [9]. III. RESULTS AND DISCUSSIONS A. Surface Morphology Study of ZnO Thin Film 1) FESEM Images Fig. 1(a) and (b) shows, at different magnifications, typical field emission scanning electron microscopy (FESEM, Quanta 200) FESEM images of as-grown ZnO nanostructures on Zn metal seed layer-coated n-Si substrates, by thermal evaporation method. It is clearly observed that the as-synthesized NWs are uniformely distributed on the whole substrate surface [9]. It may be noticed here that the as-grown nanowires are bunched