Michael B. Santos, "Narrow-gap semiconductor structures for optoelectronic applications"Dr. Michael B. Santos, Professor of Physics and the Charles L. Blackburn Chair in Engineering Physics at the University of Oklahoma, will join us on April 12, 2023 at 1:30pm in White Hall G09. He will speak on Narrow-gap semiconductor structures for optoelectronic applications. Continue reading for his abstract and biography.
The band offsets in arsenide/antimonide materials have been exploited for the development of optoelectronic devices for many years. In this talk, I will discuss recent developments in two collaborative projects on photovoltaic devices that take new advantage of the band offsets in these materials.First, we are exploring the interband cascade architecture for thermophotovoltaic applications [Sol. Energy Mater. Sol. Cells 238, 111636 (2022)]. Each stage of a multi-stage device is composed of an absorber, electron barrier, and hole barrier, all made from InAs/GaSb/AlSb multilayers. Because each absorber is thinner than the carrier diffusion length, photo-generated carriers are collected efficiently. The unipolar barriers accomplish rectification without resorting to conventional p-n junctions. The internal series resistance between stages can be negligible because transport is facilitated with a semi-metallic interface.Second, we are employing a novel strategy to harness hot-carrier effects for increasing the efficiency of a solar cell [Nature Energy 5, 336 (2020)]. In an antimonide/arsenide structure, hot electrons are stored in the upper L and X valleys of the absorber layer. The transfer of electrons to the upper valleys is accomplished through intervalley scattering and the Gunn effect. Luminescence data reveal a stable hot-carrier population at a relatively low excitation power.