9 ZnO Nanostructures for Optoelectronic Applications Ashok K. Sood 1 , Zhong Lin Wang 2 , Dennis L. Polla 3 , Nibir K. Dhar 3 , Tariq Manzur 4 and A.F.M. Anwar 5 1 Magnolia Optical Technologies Inc, 52-B Cummings Park, Suite 314, Woburn, MA 01801 2 School of Materials Science and Engineering, Georgia Institute of Technology, 771 Ferst Drive, Atlanta, GA 30332 3 DARPA/MTO, 3701 North Fairfax Drive, Arlington, VA 22203 4 Naval Underwater Warfare Center, 1176 Howell Street, Newport, RI 02841 5 Department of Electrical Engineering, University of Connecticut, Storrs, CT 06269 U.S.A. 1. Introduction ZnO is a unique material that exhibits both semiconducting and piezoelectric properties. ZnO is a unique material that exhibits both Semi conducting and piezoelectric properties. ZnO devices have been demonstrated for applications in piezoelectric pressure sensors and Pyroelectric infrared detectors [1] and Spintronic devices [2]. More recently, there has been significant effort underway for design and development of ZnO nanostructures such as ZnO nanowires for a variety of applications [3-7]. The ZnO nanostructures can be implemented in Optoelectronic, Sensors, Transducers and Biomedical applications [1, 2, 3, 4]. Use of these nanostructures, will allow building of Nanoscale nanosensors, nanocantilevers, field-effect transistors and nanoresonators for a variety of Military, Homeland Security and Commercial Applications. Due to the advancement of materials technology over the past decade, wide-band gap semiconductors such as SiC, GaN and ZnO have emerged as UV sensitive materials that have applications for UV lasers, UV Photodetector, switches, Bio-Sensors and solar cells. ZnO wide-band gap semiconductor is promising for sensor applications in the UV range. The band-gap is 3.2 eV for ZnO. Therefore, GaN and ZnO, as well as SiC are potentially good materials to cover the UV spectral band (240-280 nm), when solar radiation is completely absorbed by the ozone layer of the earth atmosphere, so the background of solar radiation at the earth surface is essentially zero. ZnO is transparent to visible light and can be made highly conductive by doping. ZnO is a versatile functional material that has a diverse group of growth morphologies. These growth morphologies have been demonstrated for nanowires (1), nanobelts (2), nanocages (3), nanocombs (4), nanosprings (5), nanorings (6), nanohelixes (7). The objective of this chapter is to review the unique ZnO nanostructure devices and characterized for optoelectronic applications. www.intechopen.com