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A milestone in petahertz electronics

We identified an important mechanism that strongly enhances the injection of carriers into the conduction band of the semiconductor GaAs when driven with close to petahertz electric fields.

by Nicolas Bigler

In a semiconductor, electrons can be excited from the valence into the conduction band via the absorption of laser light. The electron motion under the influence of a high-frequency laser field ultimately determines the material limit for high-speed device performance. Attosecond techniques extend the accessible frequency regime into the petahertz domain. Schlaepfer et al. used transient absorption spectroscopy to resolve the attosecond (10-18 s) laser-field-driven response of electrons in gallium arsenide. In addition to the excitation of electrons from one to another band (so-called inter-band transition), carriers can also be accelerated during the light-matter interaction within the individual bands due to the presence of the strong electric laser field (intra-band motion). While only the inter-band transition transfers electrons into the conduction band, Schlaepfer et al. found that the intra-band mechanism significantly enhances the number of these electrons. This finding is unexpected because intra-band motion alone is unable to produce charge carriers in the conduction band. These results represent an important step forward in understanding the light-induced electron dynamics in a semiconductor on the attosecond timescale.

Reference:  Schlaepfer, F., M. Lucchini, S. A. Sato, M. Volkov, L. Kasmi, N. Hartmann, A. Rubio, L. Gallmann and U. Keller (2018). Attosecond optical-field-enhanced carrier injection into the GaAs conduction band. Nat. Phys.: advanced online. doi: 10.1038/s41567-018-0069-0

 

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