Joan Redwing received her B.S. degree in Chemical Engineering from the University of Pittsburgh in 1986. She was as an associate staff member at General Electric Corporate Research & Development in Niskayuna, NY from 1986-1988 where she worked on the development of tungsten coated x-ray targets using chemical vapor deposition (CVD) processing. She then went to the University of Wisconsin-Madison for graduate school and received her Ph.D. in Chemical Engineering in 1994 under the direction of Prof. Thomas Kuech. Her Ph.D. thesis work focused on studying mechanisms of dopant incorporation in GaAs and AlGaAs grown by metalorganic CVD (MOCVD).
After receiving her Ph.D., Joan took a position as a research engineer with Advanced Technology Materials Inc. (ATMI) in Danbury, CT. At ATMI, she developed processes for group III-nitride epitaxy by MOCVD in a group managed by Dr. Michael Tischler. She made important contributions to the development of AlGaN/GaN two-dimensional electron gas (2DEG) heterostructures including the first report of AlGaN/GaN high electron mobility transistors (HEMTs) on SiC and identification of the role of piezoelectric polarization in determining the 2DEG carrier density. She was co-inventor on several U.S. patents related to group III-nitride LED and GaN substrate technology. In 1997, she was promoted to Manager of III-V Technology at Epitronics Inc., a subsidiary of ATMI, located in Phoenix, AZ. At Epitronics, she managed a III-V epiwafer manufacturing group which produced AlGaAs- and InGaP-based heterojunction bipolar transistor (HBT) epilayers and AlGaN/GaN HEMT epilayers.
In 2000, Joan decided to make a career change from industry to academia. She took a position as an assistant professor in Materials Science and Engineering at Penn State with a joint appointment in Electrical Engineering. At Penn State, she continued her research on group III-nitride epitaxy by MOCVD, focusing on the use of in situ wafer curvature measurement to study tensile stress in GaN epilayers grown on Si substrates and in Si doped GaN and AlGaN epilayers. She also initiated a new research direction in the synthesis of semiconductor nanowires using metal-mediated vapor-liquid-solid growth within a CVD environment. Her work in this area was aimed at studying mechanisms of doping, alloying and heterostructure formation in Si and Si/SiGe nanowires for applications in nanoscale electronics and photovoltaics. More recently, her research group has focused on the application of MOCVD to the synthesis of 2D semiconductors demonstrating wafer-scale transition metal dichalcogenide (TMD) monolayers and a unique 2D form of GaN using graphene encapsulated growth. In 2016, Joan began serving as PI and Director of the 2D Crystal Consortium (2DCC), a $20M NSF-supported Materials Innovation Platform (MIP) national user facility focused on the synthesis of 2D materials. As part of the 2DCC facility, her group is developing state-of-the-art instrumentation for MOCVD growth and characterization of 2D TMDs and related materials enabling wafer-scale synthesis, in situ characterization and post-growth ambient-controlled characterization and processing.
In addition to her research, Dr. Redwing currently serves as vice president of the American Association for Crystal Growth, is an associate editor for the Journal of Crystal Growth and a regional editor for 2D Materials. She is a Fellow of the Materials Research Society, the American Physical Society and the American Association for the Advancement of Science. She served as a Fulbright Scholar to Sweden in 2016, received the Penn State Faculty Scholar award in engineering in 2019 and gave the Nakamura Lecture at UC-Santa Barbara in 2020. She is an author on over 300 publications in refereed journals and holds 8 U.S. patents.
Research Description
Dr. Redwing’s research interests lie in the general area of electronic and optoelectronic materials synthesis and characterization with a special emphasis on metalorganic chemical vapor deposition (MOCVD) processing of semiconductor thin films and nanomaterials.
An area of current focus is the synthesis of 2D materials, specifically layered chalcogenides such as the transition metal dichalcogenides (TMDs), MX2, where M=Mo, W, Nb, etc. and X=S, Se, Te. Semiconducting TMD monolayers, which are only a few atoms thick, offer compelling properties including direct bandgap in the visible range, good carrier mobility at the ultra-thin limit, and coupled spin-valley polarization. There is growing interest in 2D TMDs for applications in nanoelectronics and 3D integration with silicon, low power biomimetic devices and photonics. Current research projects in the group are aimed at understanding fundamental mechanisms of van der Waals epitaxy of layered chalcogenides and the development of wafer-scale epitaxial growth technologies for TMD monolayers and heterostructures. This work is carried out in the NSF-supported 2D Crystal Consortium (2DCC) Materials Innovation Platform facility at Penn State on custom-designed MOCVD tools that incorporate in situ monitoring during growth and ambient controlled characterization of samples post-growth.
The development of wide bandgap group III-nitride (AlGaInN) thin films and device structures by MOCVD is an area of continuing research. Group III-nitrides are widely used in light emitting diodes for solid state lighting and in power transistors and switching devices for communications and electric vehicles. Areas of current interest include epitaxial growth and doping of ultra-wide bandgap nitrides (AlN, AlGaN), synthesis of 2D nitrides including hBN and 2D GaNx and patterned growth of nanowire arrays for vacuum nanoelectronics. This work is carried out using a custom-designed MOCVD system capable of growth at temperatures up to 1500oC that includes a multibeam optical stress (MOS) sensor system for in-situ measurements of film stress due to heteroepitaxy and doping.