ZnO is a promising wide band gap semiconductor. It has been also emerging as an important multifunctional oxide. Through proper doping or alloying, ZnO–based materials can be made transparent and conductive, piezoelectric, or ferromagnetic. ZnO based single crystal nanostructures can be grown on various substrates at relatively low temperature. We have integrated ZnO based multilayers and nanostructures to construct novel devices. High quality epitaxial ZnO and MgxZn1-xO films are grown on r-plane sapphire substrates by metaloganic chemical vapor deposition (MOCVD). The non-polar a-plane ZnO-based structures are used to make various devices, including high speed UV detectors, Schottky diodes, and field-effect transistors (FETs). ZnO semiconductor and piezoelectric films are integrated into the multilayer structures to make the tunable devices, such as a RF phase shifter and the wireless UV detector using the acousto-electric and acousto-optical interactions, respectively.
Single crystal ZnO nanotips are grown on various substrates, including Si, GaN, glass, and metals. The ZnO nanotips exhibit dominant free excitonic transition and enhanced luminescence efficiency. A 3-D electrode is developed by integrating a 2-D ZnO based transparent conductive oxide (TCO) film with 1-D ZnO nanotips array by sequential MOCVD growth. The solar cells which use such 3-D ZnO photoelectrodes show better efficiency and faster speed. The integration of the 3-D ZnO electrodes with a GaN LED enhances the device’s photon extraction. The recent progress on the ZnO nanostructure-based resistive switching and nonvolatile memory devices will also be discussed. The integrations of the ZnO memristor with ZnO diode (1D1R) and with ZnO thin film transistor (1T1R) form the basic building blocks. for the reconfigurable electronics and optoelectronics. The technology has broad applications in ultra high density nonvolatile memory, reconfigurable electronics and optoelectronics, smart sensor and sensor networks.
Dr. Lu is a Paul S. and Mary W. Monroe Faculty Scholar, the endowed chair professor and chairman in the Department of Electrical and Computer Engineering at Rutgers. His major research field is micro- and nano-electronic materials and devices. Professor Lu’s group has grown high quality epitaxial non-polar ZnO and MgxZn1-xO films and single crystal ZnO nanostructures by MOCVD. He has demonstrated various ZnO devices, including Schottky diode, optically addressed high contrast and high speed UV light modulator, high speed ZnO MSM photoconductive and photovoltaic UV photodetectors, nano-SAW and nano-BAW biosensors, wireless UV detector, nano-ZnO/GaN LED, ZnO 3-D photoelectrodes consisting of TCO & nanotips for solar cells, and monolithically integrated tunable SAW (MITSAW) chips. Dr. Lu’s group has also conducted research on high frequency RF components for telecommunication and sensors. He has published over 200-refereed articles, and received 18 U.S. patents. Dr. Lu is a co-organizer of the 2nd and 3rd International ZnO Workshops (Dayton, 2002, and Sendai, Japan, 2004), International organizing committee member of the 4th International Workshop of ZnO and Related Materials (German, 2006), and Co-Chairman of the 5th International Workshop of ZnO and Related Materials. He has been an organization committer member and a co-chairman of ZnO session in EMC since 2005. In 1991, Dr. Lu received NSF Research Initiation Award. He received the 1993 Warren I. Susman Award for Excellence in Teaching, the highest teaching award at Rutgers. In 1994 he received the Rutgers University Board of Trustees Research Fellowship award for Scholarly Excellence, and the IEEE Outstanding Student Counselor and Advisor Award in 1995. In 2002, Prof. Lu was one of the two recipients of the Rutgers Teacher-Scholar award.