Transient response of photoexcited electrons: negative and oscillating current

TL;DR

This paper theoretically investigates the transient photocurrent of photoexcited electrons, revealing phenomena like negative conductivity and oscillations, and examines how scattering affects these effects.

Contribution

It introduces a theoretical analysis of transient electron response showing negative conductivity and oscillations, including effects of elastic scattering.

Findings

Transient absolute negative conductivity occurs below optical phonon energy.

Periodic oscillations of electric current appear after streaming distribution formation.

Elastic scattering quenches the negative conductivity and oscillations.

Abstract

Time-dependent current of the electrons excited in the conduction band after ultrafast interband photogeneration is studied theoretically. The transient photocurrent is calculated for the nonlinear regime of response to a stationary electric field. The response demonstrates transient absolute negative conductivity when the electrons are excited slightly below the optical phonon energy, while the periodic oscillations of the electric current appear after formation of the streaming distribution. The quenching of these peculiarities by the elastic scattering of electrons is also considered.