Advancing materials and devices has been the core foundation of most of the technology evolution throughout human history.  In our research group, we are interested in tackling challenges mainly in the fields of information technology and human health through materials and device innovation.  Our research program currently consists of the following three themes: 1) nano‑electronics; 2) bio‑electronics; 3) materials surfaces and interfaces.

1. Nano-electronics

Silicon-based metal–oxide–semiconductor field-effect transistors (MOSFET) have been the workhorse for the remarkable expansion of Research1.1integrated circuits (ICs) industry since its first introduction.  In the past decade, however, the semiconductor industry has faced significant challenges from the paradox between performance and power.  The goal of the nano-electronics theme is to explore novel semiconductor nano-materials and device architectures which have the potential to reduce the power consumption drastically.  Our interests span from nanoscale III-V compound semiconductors to 2D layered chalcogenides, from tunneling field effect transistors to neuromorphic devices.

Recent papers:

1. H. Fang, S. Chuang, T. C. Chang, K. Takei, T. Takahashi, A. Javey, “High-Performance Single Layered WSe2 p-FETs with Chemically Doped Contacts“, Nano Letters, 12, 3788-3792, 2012.
2. J. Nah†, H. Fang†, C. Wang, K. Takei, M. H. Lee, E. Plis, S. Krishna, A. Javey, “III–V Complementary Metal–Oxide–Semiconductor Electronics on Silicon Substrates“, Nano Letters, 12, 3592-3595, 2012.
3. H. Fang, S. Chuang, K. Takei, H. S. Kim, E. Plis, C.-H. Liu, S. Krishna, Y.-L. Chueh, A. Javey, “Ultrathin-Body, High-Mobility InAsSb-on-Insulator Field-Effect Transistors”, IEEE Electron Device Letters, 33(4), 504-506, 2012.
4. S. Chuang, R. Kapadia, H. Fang, T. C. Chang, W.-C. Yen, Y.-L. Chueh, A. Javey, “Near-ideal electrical properties of InAs/WSe2 van der Waals heterojunction diodes“, Applied Physics Letters, 102, 242101, 2013. (cover article).
5. P. Zhao, S. Desai, M. Tosun, T. Roy, H. Fang, A. Sachid, M. Amani, C. Hu, A. Javey, “2D Layered Materials: From Materials Properties to Device Applications”, IEEE IEDM, 27.3.1 – 27.3.4, 2015.

2. Bio-electronics

Biology is usually soft, curvilinear and wet, while electronics are usually rigid, flat and dry. Technologies that bridge this gap can open unprecedented opportunities in biology and health care. Recently we have developed a class of flexible active sensing matrix with a capacitively coupled sensing strategy that combines: i) high performance multiplexed electrical sensing capability of up to 1000 units; ii) great flexibility that can wrap around heart and brain tissue; iii) superior device longevity that comes from an innovative encapsulation frNeural-interfaceom thermally grown SiO2 layer. We have successfully applied this system into two areas: i) monitoring micro electrocorticographic (µECoG) activity in the brain of non-human primate, and ii) mapping epicardial physiology on Langendorff-perfused rabbit heart model.
In this theme, we aim to build next generation electronic and optoelectronic tools and biomedical devices for various applications, such as brain activity mapping, diagnosis and treatment of neurological disorders and heart diseases, and neuro-prosthesis.  Specifically, our research efforts will be focused on: i) very-large-scale integration of nano-electronic and nano-photonic devices and ii) novel nanoscale devices for brain recording and stimulation, with a long-term goal towards wireless communication.

Recent papers:

1. H. Fang, K.J. Yu, C. Gloschat, Z. Yang, E. Song, C.-H. Chiang, J. Zhao, S.M. Won, S. Xu, M. Trumpis, Y. Zhong, S.W. Han, Y. Xue, D. Xu, S.W. Choi, G. Cauwenberghs, M. Kay, Y. Huang, J. Viventi, I.R. Efimov and J.A. Rogers, “Capacitively Coupled Arrays of Multiplexed Flexible Silicon Transistors for Long-Term Cardiac Electrophysiology“, Nature Biomedical Engineering, 1, 0038, 2017.
2. H. Fang, J. Zhao, K. Yu, E. Song, A.B. Farimani, C.H. Chiang, X. Jin, Y. Xue, D. Xu, W. Du, K.J. Seo, Y. Zhong, Z. Yang, S. Won, G. Fang, S.W. Choi, S. Chaudhuri, Y. Huang, M. Ashraful Alam, J. Viventi, N.R. Aluru, J.A. Rogers, “Ultra-thin, Transferred Layers of Thermally Grown Silicon Dioxide as Biofluid Barriers for Bio-Integrated Flexible Electronic Systems”, Proceedings of the National Academy of Sciences (PNAS), 113, 11682-11687, 2016.
3. K.J. Yu, D. Kuzum, S.-W. Hwang, B.H. Kim, H. Juul, N.H. Kim, S.M. Won, K. Chiang, M. Trumpis, A.G. Richardson, H. Cheng, H. Fang, M. Thompson, H. Bink, D. Talos, K.J. Seo, H.N. Lee, S.-K. Kang, J.-H. Kim, J.Y. Lee, Y. Huang, F.E. Jensen, M.A. Dichter, T.H. Lucas, J. Viventi, B. Litt and J.A. Rogers, “Bioresorbable Silicon Electronics for Transient Spatiotemporal Mapping of Electrical Activity from the Cerebral Cortex”, Nature Materials, 15, 782-791, 2016.

3. Materials surfaces and interfaces

Enabling by new materials processing and device fabrication methodologies, we often create unprecespl_4dented material systems, such as free-standing semiconductor nano-membrane, 2D-2D van der Waal semiconductor heterostructure, and thermal SiO2/tissue interface. These new materials/device have the real potential to unlock new technologies and shift paradigms. They often require deep probing to understand various physics and material science at the materials surfaces and interfaces.  In theme 3, we study many electronically, optoelectronically and chemically dynamic phenomena, such as charge transfer, electron-phonon interactions, electron generation/recombination, from advanced microscopic and spectroscopic techniques.  We seek to understand these phenomena, engineer from the fundamental material structure level to control these properties, and achieve the tailored materials and device functionality.

Recent papers:

1. H. Fang, C Battaglia, C. Carraro, S. Nemsak, B. Ozdol, J. S. Kang, H. A. Bechtel, S. B. Desai, F. Kronast, A. A. Unal, G. Conti, C. Conlon, G. K. Palsson, M. C. Martin, A. M. Minor, C. S. Fadley, E. Yablonovitch, R. Maboudian, A. Javey. “Strong interlayer coupling in van der Waals heterostructures built from single-layer chalcogenides“, Proceedings of the National Academy of Sciences (PNAS), 111 (17), 6198-6202, 2014.
2. H. Fang, H. A. Bechtel, E. Plis, M. C. Martin, S. Krishna, E. Yablonovitch, A. Javey, “Quantum of Optical Absorption in Two-Dimensional Semiconductors”, Proceedings of the National Academy of Sciences (PNAS), 110, 11688-11691, 2013.
3. K. Takei†, H. Fang†, S. B. Kumar†, R. Kapadia, Q. Gao, M. Madsen, H. S. Kim, C.-H. Liu, Y.-L. Chueh, E. Plis, S. Krishna, H. A. Bechtel, J. Guo, A. Javey. “Quantum Confinement Effects in Nanoscale-Thickness InAs Membranes“, Nano Letters, 11, 5008–5012, 2011.