Gordon E. Moore Medal for Outstanding Achievement in Solid State Science and Technology
Wide Bandgap Semiconductors for Sensing Applications
by Fan Ren
Monday, May 13, 2013 | Toronto, Ontario, Canada
The biosensor market is forecasted to reach $4.4 billion by 2014 in the U.S. This growth will be sustained especially by a high demand for biosensors that can be used for medical applications such as glucose monitoring, biomarker detection for infectious diseases, and cancer diagnosis. In addition, there will be strong demand for biosensors with applications in biodefense, environmental monitoring, food, and pharmaceutical industries. There is currently great interest in developing sensors that could be used in point-of-care applications or on-field measurements to reduce medical costs and emergency room visits. Transistor based sensors are promising for these applications. These sensors need to have high precision, compact size, fast response time, and be sensitive to small amounts of biological material.
Semiconductor properties including current, potential, and impedance characteristics that can be used to directly measure chemical or physical stimuli on the semiconductor surface. The wide energy bandgap semiconductor gallium nitride (GaN) material system is attracting much interest for commercial applications of green, blue, and UV light emitting diodes (LEDs), laser diodes, as well as high speed and high frequency power devices. Due to the wide-bandgap nature of the material (3.2 eV for GaN as compared to 1.12eV for Si), it is very thermally stable, and electronic devices can be operated at temperatures up to 500ºC. The GaN based materials are also chemically stable, and no known wet chemical etchant can etch these materials; this makes them very suitable for operation in chemically harsh environments. GaN based sensors for gas and chemical detection as well as medical applications will be presented.
Fan Ren received a BS degree in applied chemistry from Feng Chia University in 1975; an MS degree in chemical engineering from National Cheng Kung University in 1978; an MS degree in polymer science and engineering, and a PhD in inorganic chemistry from Brooklyn Polytechnic in 1991. He joined the University of Florida (UF) in 1998 where he is a Distinguished Professor in the Department of Chemical Engineering and an ExxonMobil Gator Chemical Engineering Alumni Chair Professor. Prior to joining UF, Ren worked at Bell Labs where he was a key figure in developing GaAs metal semiconductor field effect transistors grown on silicon substrate, carbon-doped InGaP/GaAs heterojunction bipolar transistors, and enhancement mode GaAs and InGaAs metal oxide semiconductor (MOS) field effect transistors. At UF, Dr. Ren has primarily focused on fabrication processes for high breakdown voltage GaN based Schottky and MOS diodes, as well as AlGaN/GaN high electron mobility transistor based sensors.
Dr. Ren’s publications have been cited over 13,500 times in the literature. He is a Fellow of ECS, APS, AVS, IEEE, MRS, and SPIE. He is the co-author of more than 820 journal publications and co-inventor of 31 issued patents. He received the 2008 Electronics and Photonics Division Award from ECS, the 2010 Albert Nerken Award from AVS and the 2010 NASA Tech Brief Initial Award.
Summary of the Lecture
After being introduced to the audience by the ECS President Fernando Garzon, Dr. Ren began his award lecture acknowledging his collaborator and nominator, Steve Pearton.
The lecture focused on the development of AlGaN/GaN junction-based transistors (HEMTs) for gas and bio-sensing applications. In general, the HEMT gate can be coated with selective agents for the gaseous and ionic solution analytes. The sensing mechanism is based on altered barrier height in the transistor device because of analyte interactions. The resultant signal may be amplified to provide for very high sensitivity. The use of semiconductor-based solid-state devices naturally lends to “fieldable” and remotely-accessible sensors. He gave examples of recent work from his group in this area for sensitive and selective detection of several families of analytes based on biomolecules (e.g., kidney injury biomarkers and endocrine disruptor biomarkers in fish); mercury; and gases such as hydrogen, CO and CO2, arsenic, methane, pesticides etc. In particular a field example based on leak detection of hydrogen in an electric car was interesting to this writer (KR). Dr. Ren pointed out that the biosensor market is poised to reach $4.4 billion by 2014 in the U.S. He also underlined the strong demand for biosensors in divergent market sectors in biodefense, environmental monitoring, food, and pharma. Sensors that are adaptable to point of-care or on-field use and have high precision, compact size, fast response, and high selectivity would be particularly relevant to such application needs.
Dr. Ren’s award talk provided a clear demonstration of how AlGaN/GaN sensors fulfilled these requirements.