Prof. Christos Flytzanis, Laboratoire Pierre Aigrain, Paris

Abstract:

We present  an experimental and theoretical study (*)of charge transport in semiconductors, specifically in bulk GaAs, in single-component electron and hole plasma , n- and p-doped samples respectively, and in photo-generated electron-hole plasma.  We evidence  the transition from ballistic to diffusive (drift-like) regime and the role played by the quantum coherences and quantum-kinetic  scattering processes  there .  

The transport is initiated with ultra-short THz transients  with electric field amplitudes up to 100-300 MV/cm and followed up and mapped with an electro-optic sampling technique.  The theoretical analysis is conducted in terms of a quantum kinetic model of the transient dielectric constant of the electron-hole plasma that includes coherent polaron and Bloch state dynamics and also provides a description of quantum friction ; it evidences time dependent screening of the external field by the carrier plasma that can be accounted for in terms  of  local field and depolarization effects.

Along with their  intrinsic fundamental interest the  study of these regimes has a relevance on the performances of ultrafast optoelectronic semiconductor devices as well.

(*) study  performed at the Max Born Institute, Berlin, Germany.

Bowlan P. et al, Phys. Rev. Letts 107, 256602 (2011); Phys. Rev. B 85, 165206  (2012)