M. Roger Clapp University Professor and Chair Department of Physics
Rockefeller Building 220
B.A., Middlebury College (1975)
Ph.D., Massachusetts Institute of Technology (1982)
Experimental Condensed Matter Physics
The binary nitride semiconductors (gallium nitride, aluminum nitride and indium nitride) have brought about a revolution in lighting technology. We have light emitting diodes that fit into incandescent light sockets and, though currently they cost more than incandescent bulbs, last twenty times as long and use roughly one-tenth the amount of power for the same amount of light produced. The binary nitrides are much more robust than is silicon, so they are also taking over much of the power electronics market, which is even larger than the lighting market.
Our research focuses on experimental and theoretical studies of one class of complex nitride semiconductors that are related to the binary nitrides—the so-called “heterovalent ternary nitrides”. Two of the many examples are zinc germanium nitride and magnesium tin nitride. The lattices of these crystalline materials are related to that of the binary nitrides. The atoms are arranged similarly, but the lattices are more complex. We seek to explore new physical phenomena that emerge from this greater complexity, and to incorporate these materials into new devices that take advantage of their unique properties.
In addition, much of our research concentrates on developing new growth methods for these materials. Since many of these are composed entirely of abundant, nontoxic and inexpensive materials, unlike, for example, gallium and indium, one additional motivation for our research is to seek ways to replace materials toxic and expensive elements with these.
“Raman study of the vibrational modes in ZnGeN2 (0001), Eric W. Blanton, Mark Hagemann, Keliang He, Jie Shan, Walter R.L. Lambrecht and Kathleen Kash, J. Appl. Phys. 121, 055704 (2017). http://doi.org/10.1063/1.4975040
“Vapor-liquid-solid synthesis of ZnSnN2”, Paul C. Quayle, Grant T. Junno, Keliang He, Eric W. Blanton, Jie Shan and Kathleen Kash, Phys. Status Solidi B, 1600718 (2017).
“Characterization and Control of ZnGeN2 Cation Lattice Ordering”, Eric W. Blanton, Keliang He, Jie Shan and Kathleen Kash, J. Crystal Growth 461, 38 (2017). https://doi.org/10.1016/j.crysgro.2017.01.008
“Disorder effects on the band structure of ZnGeN2: Role of exchange defects”, D. Skachkov, P.C. Quayle, K. Kash, and W.R.L. Lambrecht, Phys. Rev. B94, 205201 (2016). https://journals.aps.org/prb/abstract/10.1103/PhysRevB.94.205201
“Designs of blue and green light-emitting diodes based on type-II InGaN-ZnGeN2 quantum wells”, Lu Han, Kathleen Kash and Hongping Zhao, Journal of Applied Physics 120, 103102 (2016). http://dx.doi.org/10.1063/1.4962280
“Charge-neutral disorder and polytopes in heterovalent wurtzite-based ternary semiconductors: The importance of the octet rule”, Paul C. Quayle, Eric W. Blanton, Atchara Punya, Grant T. Junno, Keliang He, Lu Han, Hongping Zhao, Jie Shan, Walter R.L. Lambrecht and Kathleen Kash, Phys. Rev. B91, 205207 (2015).
“Synthesis, lattice structure and band gap of ZnSnN2”, Paul Quayle, Keliang He, Jie Shan, Kathleen Kash, MRS Communications (2013).http://dx.doi.org/10.1557/mrc.2013.19.
“ZnGeN2: The Effects of Growth Conditions on Morphology, Ordering and Optical Properties”, E. Blanton, P. Zhao, K. He, J. Shan, H. Zhao and K. Kash, Online Proceedings of the 2012 Fall Meeting of the MRS Society, Photovoltaic Technologies—Materials, Devices and Systems E19.93 (2013).
“Thermodynamic Properties of Gallium Nitride”, Timothy J. Peshek, John C. Angus, Kathleen Kash, J. Crystal Growth 322, 114 (2011).http://dx.doi.org/10.1016/j.crysgro.2011.09.040
“Electrochemical Charge Transfer to Diamond and Other Materials”, Vidhya Chakrapani, John C. Angus, Kathleen Kash, Alfred B. Anderson, Sharvil Desai and Gamini U. Sumanasekeran, Proceedings of Symposium J of the 2009 Fall Meeting of the Materials Research Society (Boston, MA, November 30-December 4, 2009); Vol 1203, 1203-J07-01. http://dx.doi.org/10.1557/PROC-1203-J07-01
“Vibrational modes in ZnGeN2: Raman study and theory”, Timothy J. Peshek, Tula Ram Paudel, Kathleen Kash and Walter R.L. Lambrecht, Phys. Rev. B 77, 235213 (2008). http://link.aps.org/abstract/PRB/v77/e235213
“Experimental Investigation of the Enthalpy, Entropy and Free Energy of Formation of GaN”, Timothy J. Peshek, John C. Angus, and Kathleen Kash, Journal of Crystal Growth 311, 185 (2008). http://dx.doi.org/10.1016/j.jcrysgro.2008.09.203
“Synthesis and Characterization of ZnGeN2 grown from Elemental Zn and Ge Sources”, K. Du, C. Bekele, C.C. Hayman, J.C. Angus, P. Pirouz, K. Kash, J. Crystal Growth 310, 1065 (2008). http://dx.doi.org/10.1016/j.jcrysgro.2007.12.042