We are primarily interested in the optical and electronic characterization of currently important large bandgap semiconductors such as AIN, GaN and SiC. Great emphasis in our research is placed on a close collaboration with the world`s most outstanding growers of single crystal boule material or single crystal epitaxial films. Most recently we have started to learn how to prepare and study single crystal porous SiC. Many new morphologies have been discovered in both n and p type SiC, and applications to medicine, gas sensing and fuel cells are being explored.
We study optical and electrical properties by a variety of techniques, and also put considerable effort into preparation of specialized samples. Regarding nanoscience and technology, examples of relevant work include the fabrication and investigation of porous SiC and investigations of polytype inclusions which behave as quantum wells.
We are also investigating SiC as a tool for nano-machining applications, as a substitute for diamond, towards applications for which diamond does not work well or at all.
"Phonon dispersion curves by raman scattering in SiC, polytypes 3C, 4H, 6H, 15R, and 21R," Feldman, D.W., Parker, J.H., Choyke, W.J., Patrick, L., Physical Review 173, no. 3 (1968)
"Deep defect centers in silicon carbide monitored with deep level ransient spectroscopy," Dalibor, T., Pensl, G., Matsunami, H., Kimoto, T., Choyke, W.J., Schoner, A., Nordell, N., Physica Status Solidi (A) Applied Research 162, no. 1 (1997)
"An investigation of the properties of cubic CaN grown on GaAs by plasma-assistied molecular-beam epitaxy," Strite, S., Ruan, J., Li, Z., Salvador, A., Chen, H., Smith, D.J., Choyke, W.J., Morkoc, H., Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures 9, no. 4 (1991)
"Electrical and optical characterization of SiC," Pensl, G., Choyke, W.J., Physica B: Physics of Condensed Matter 185, no. 1-4 (1993)
"Comparative electron spectroscopic studies of surface segregation on SiC(0001) and SiC(000-1)," Muehlhoff, L., Choyke, W.J., Bozack, M.J., Yates Jr., J.T., Journal of Applied Physics 60, no. 8 (1986)
"Newly resolved phonon-assisted transitions and fine structure in the low temperature wavelength modulated absorption and photoluminescence spectra of 6H SiC," Klahold, W.M., Choyke, W.J., Devaty, R.P. (2019) Materials Science Forum, 963 MSF, pp. 341-345.
"High resolution optical spectroscopy of free exciton and electronic band structure near the fundamental gap in 4H SiC." Klahold, W.M., Choyke, W.J., Devaty, R.P. Materials Science Forum 924 MSF, pp. 239-244. (2018).
"HIGH ENERGY ION BOMBARDMENT SIMULATION FACILITY AT THE UNIVERSITY OF PITTSBURGH." PITTSBURGH.McGruer, J.N., Choyke, W.J., Doyle, N.J., Spitznagel, J.A.
"New evidence for the second conduction band in 4H SiC." Klahold, W., Tabachnick, C., Freedman, G., Devaty, R.P., Choyke, W.J. Materials Science Forum 897 MSF, pp. 250-253. (2017).
"Annealing of electron irradiated, thick, ultrapure 4H SiC between 1100°c and 1500°c and measurements of lifetime and photoluminescence." Klahold, W.M., Devaty, R.P., Choyke, W.J., (...), Kimoto, T., Ohshima, T. Materials Science Forum 778-780, pp. 273-276. (2014).
"Determination of the phonon dispersion of zinc blende (3C) silicon carbide by inelastic x-ray scattering," J. Serrano, J.Strempfer, M. Cardona, M. Schwoerer-Böhning, H. Requardt, M. Lorenzen. B. Stojetz, P. Pavaone and W.J.Choyke, Appl. Phys. Lett. V80, 4360, (2002)
"Determination of the electric field in 4H/3C/4H quantum wells due to spontaneous polarization in the 4H SiC matrix," S. Bai, R.P. Devaty, W.J. Choyke, U. Kaiser, G. Wagner, and M.F. MacMillan, Appl. Phys. Lett. V83, 3171, (2003)
"Identification of the Carbon Dangling Bond Center at the 4H/-SiC/SiO2 Interface by an EPR Study in Oxidized Porous SiC," J.L. Cantin, H.J. von Bardeleben, Y. Shishkin, Y.Ke, R.P. Devaty and W.J.Choyke, Phys. Rev. Lett. V92, 015502-1, (2004)
"Photoelectrochemical etching of n-type 4H Silicon Carbide," Y. Shishkin, W.J. Choyke and R.P. Devaty, Jour. Appl. Phys. V96, 3311, (2004)