Alan Bristow, PhD
Professor
Department of Physics and Astronomy
West Virginia University
Friday, September 13, 2024
Pulsed terahertz (THz) electromagnetic radiation is well suited to probe a material’s complex AC conductivity. In solids, charge transport conforms to conduction models that are parameterized by the carrier concentration and scattering time, which are governed by carrier-carrier or carrier-lattice interactions. THz pulses, generated by nonlinear optical conversion from short-pulsed IR laser light [1], measure AC conductivity non-destructively to give results complementary to Hall-effect measurements without the need for contacts or strong magnetic fields. Similarly, AC photoconductivity measures the excited-state transport and subsequent relaxation/recombination dynamics resulting from optical excitation pulses from the same source laser. Presented here are examples that include temperature-dependent AC conductivity of bulk semiconductor crystals to determine the scattering mechanisms due to phonons and defects [2], and pump-photon-energy- and temperature-dependent AC photoconductivity of type-II aligned superlattices to determine the hot-carrier dynamics via Auger and radiative recombination [3], and transport via ambipolar diffusion [4] (as illustrated in the figure).The examples showcase a spectroscopic approach to monitor the behavior of materials and devices for applications in sensing, communications, optoelectronics, and photovoltaics.
Professor Alan D. Bristow received a Ph.D. in Physics from the University of Sheffield in 2004. He was a Postdoctoral Fellow at the University of Toronto and then a Research Associate at JILA (a division of the National Institute of Standards and Technology at the University of Colorado-Boulder). Dr. Bristow was an Adjunct Instructor at Colorado School of Mines in 2009 and joined the faculty of West Virginia University in 2010, where he leads the Ultrafast Nanophotonics Group. Dr. Bristow is a Senior Member of Optica (formerly OSA), a Feature Editor for Optical Materials Express, and an Associate at the National Institute of Standards and Technology. He serves as the Associate Chair of Graduate Studies and Research at WVU’s Department of Physics and Astronomy.