Regensburg 2016 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 36: Poster Ib

HL 36.35: Poster

Tuesday, March 8, 2016, 15:00–19:00, Poster A

Anisotropy measurement using ultrafast photocurrents — •Christian Schmidt, Shekhar Priyadarshi, and Mark Bieler — Physikalisch-Technische Bundesanstalt, Braunschweig, Germany

The linear surface magneto-photocurrent (LSMC) is based on an optically induced anisotropic carrier distribution which is scattered asymmetrically at the surface of semiconductors [1]. Here, we investigate the LSMC induced in bulk GaAs by optical femtosecond excitation on a sub-picosecond time scale. For this we detect its THz radiation via electro-optical sampling [2]. Comparing the LSMC measurements with a time-dependent model of the LSMC we are able to extract the anisotropy relaxation time from our measurements.

We found a double exponential decay of the anisotropy with the fast time constant being on the order of 10 fs and the slow time constant ranging from 100 fs to 190 fs. We attribute the fast and slow relaxation times to anisotropy relaxation of heavy holes and electrons, respectively. Variations of the photocarrier density in the range of 10¹⁵ cm⁻³ to 5×10¹⁷ cm⁻³ indicate that phonon-carrier scattering is the major anisotropy relaxation mechanism for electrons. Our data compares well to previously reported anisotropy relaxation times ranging from 30 fs to 190 fs [3], [4] and shows that the LSMC is a novel intrinsic probe for anisotropy relaxation in semiconductors.

[1] V.L. Alperovich et al., JETP Lett. 49, 702 (1989).

[2] C.B. Schmidt et al., Appl. Phys. Lett. 106, 142108 (2015).

[3] J.L. Oudar et al., Phys. Rev. Lett. 53, 384 (1984).

[4] M.T. Portella et al., Appl. Phys. Lett. 60, 2123 (1992).