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Skewed functional processes and their applications

Indium Gallium Zinc Oxide and other Transparent Conducting Oxides For Transparent and Flexible Electronics

Abstract

Traditional electronics have been limited to crystalline substrates, which by their crystalline nature are fragile and inflexible. Traditional semiconductor materials like gallium arsenide and silicon are also opaque to visible light. Recently we have been investigating a new class of semiconductor materials that can be both amorphous allowing them to be deposited on flexible substrates or amorphous substrates such as glass, and transparent to visible light allowing you to see through them like a piece of glass. Furthermore the electron mobility of these materials is 10 to 100 times faster than that of conventional amorphous electronic materials such as amorphous silicon, or organic materials such as pentecene. In addition to the superior electronic properties of these new materials the also appear to be more stable to environmental factors than more traditional materials being investigated. Thus it is easy to imagine transparent electronic devices in a wide variety of applications ranging from inexpensive consumer electronics to demanding industrial and military applications. However, at the present stage of development it is clear that further research and development is needed to find optimal choice of transparent conducting oxide materials. In this talk we will describe our approach to investigating the InGaZnO material system for transparent transistors and the uses we are finding for it as a material for other transparent optoelectronic devices.

       The majority of the talk will focus on our investigations into amorphous InGaZnO deposited at room temperature by pulsed laser deposition as the channel for an all oxide transistor with transparent InGaZnO contact and an ATO/ITO dielectric and gate. High quality enhancement mode transistors were produced with off currents on the order of 0.1 picoamps, on/off ratios of 5 x 10⁷, threshold voltages of 2 V and channel mobilities of 11 cm²V^-1s^-1. Control of the threshold voltage by varying the channel thickness and the influence of varying the gate dielectric were investigated    

     In addition to the InGaZnO material system, the use of gallium oxide as a host for rare earth dopants for visible light emitters will be presented, as well as the fabrication of a ZnO optical modulator.

Acknowledgements: I would like to thank the students who have been working on this project Arun Suresh, Patrick Wellenius, Anuj Dhawan, Praveen Gollakota  and Roy Zhang, Professor Leda Lunardi who co-chaired Praveen with me and has made numerous constructive suggestions on these projects, as well as Professors Veena Misra, Doug Barlage and Mark Johnson who’s hallway conversations on materials and devices greatly add to the creative environment at the Montieth Research Center.

Bio for John Muth

John Muth received a B.S. degree in Applied Engineering Physics from Cornell University in 1988.  From 1988-1993 he served in the United State Navy as a submarine officer, with responsibilities including tactical operation of the submarine and supervision of the nuclear reactor. Upon leaving the Navy, he received a Ph.D. in solid state physics  in 1998 at North Carolina State University for "Optical Characterization of GaN and ZnO" While in graduate school he co-founded a software company that eventually grew to 60 people and has released 6 products, After staring at computer screens a lot, he decided to pursue an academic career at North Carolina State University joining the faculty in the nanoelectronics and photonics area in 2000. 

Dr. Muth's technical skills include the optical characterization of materials and the fabrication of novel optoelectronic devices. One major focus is the deposition of novel oxide materials by pulsed laser deposition and the fabrication of transparent electronic and photonic devices.  He has published over 70 peer reviewed papers and conference proceedings and has five granted patents. He currently continues his work on wide band gap semiconductors, novel oxide materials and teaches undergraduate and graduate courses in Photonics and Optical Communications.