Regensburg 2022 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 40: THz and MIR Physics in Semiconductors

HL 40.6: Talk

Friday, September 9, 2022, 11:15–11:30, H33

Probing Free Electrons in InSb with Terahertz Shockwave Spectroscopy — •Peter Fischer, Gabriel Fitzky, Davide Bossini, Alfred Leitenstorfer, and Ron Tenne — Department of Physics and Center for Applied Photonics, University of Konstanz, D-78457 Konstanz, Germany

The Auger process, a non-radiative three-particle recombination, is critical especially in narrow-band semiconductors where it sets a fundamental efficiency limit for optoelectronic applications. Since their characteristic response frequencies fall within a broadband interval in the terahertz and mid-infrared range, quantitative studies of the electron dynamics in these materials remain challenging. Here, we demonstrate a new pump-probe technique able to monitor the free carrier plasma by observing its signature in the transient terahertz reflectivity spectrum. A broadband terahertz source, providing at the same time maximum temporal resolution, emerges from slicing the electric-field transient on a subcycle time scale, effectively generating a shockwave. Applying this transient to InSb after interband excitation, we find that the Auger-recombination coefficient increases by a factor of two from room temperature to 4.2 K. Furthermore, the importance of electron trapping to accurately model carrier dynamics is illustrated. Our approach exclusively targets the response of free charge carriers, disentangled from other contributions by e.g. bound excitons. Therefore, it offers a tool complementary to established time-resolved techniques.