Noise properties of a single ZnO nanowire device
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1080-O17-08
Noise properties of a single ZnO nanowire device Soo Han Choi1,2, Dong Wook Kim1, Do Young Jang1, Hyun Jin Ji1, Sang Woo Kim3, So Jung Park4, Seung Eon Moon4, and Gyu Tae Kim1 1 School of Electrical Engineering, Korea University, Seoul, Korea, Republic of 2 CAE, Semiconductor R&D Center, Samsung Electronics Co. Ltd., Hwasung, Korea, Republic of 3 School of Advanced Materials and System Engineering, Kumoh National Institute of Technology, Gumi, Korea, Republic of 4 Electronics and Telecommunications Research Institute, Daejeon, Korea, Republic of ABSTRACT The low frequency noise of individual ZnO nanowire (NW) field effect transistors (FETs) exposed to air is systematically characterized. The measured noise power spectrum shows a classical 1/f type. The noise amplitude is independent of source-drain current and inversely proportional to gate voltage. The extracted Hooge’s constant of ZnO NW is found to be 6.52 × 10-3. In addition, the low frequency noise of ZnO NW according to NW resistance and contact property are investigated. The noise amplitude is proportional to the square of ZnO NW resistance. If a sample shows a nonlinear current-voltage (I-V) characteristic due to a poor electrical contact, the noise power spectrum is proportional to the third power of current instead of the square of current. INTRODUCTION Zinc oxide whose band gap is about 3.36eV at room temperature, is intrinsically n-type because the oxygen vacancies act as dominant donors. Because of high mobility of charge carriers and large surface-to-volume ratio, ZnO nanowire (NW) has a potential application as field effect transistors (FETs) [1] and gas sensors [2]. Since the low frequency noise contains the important information about charge transport and fluctuation [3], the understanding of low frequency noise is helpful to achieve the practical electronic and sensor applications. In this paper, ZnO NWs synthesized by a vapor liquid solid (VLS) process are configured as FETs and their noise properties are characterized. The Hooge’s constant in the noise characteristics is extracted from the gate dependence of noise amplitude. Additionally, the noise properties caused by the NW resistance and contact property are characterized. The noise amplitude is proportional to the square of NW resistance. The sample having the nonlinear current-voltage (I-V) characteristics because of a bad contact shows a different noise property compared with the sample with linear I-V characteristics. EXPERIMENT Synthesis of ZnO nanowires Single-crystalline ZnO NWs are synthesized via a vapor liquid solid (VLS) process. Undoped GaN epilayers with 4-µm thickness is grown by metalorganic chemical vapor
deposition (MOCVD) on c-Al2O3 substrates. Prior to the NW growth in a tube furnace, an Au thin layer (3nm) deposited on the GaN epilayer is used as a catalyst or the realization of highly aligned NWs. High-yield synthesis of ZnO NWs is achieved by evaporating a mixture of ZnO (99.999% purity) and graphite (99.99% purity) powders (1:1) in an Ar ambient atmosphere
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