Spin-photocurrent in p-SiGe quantum wells under terahertz laser irradiation

TL;DR

This paper investigates the circular photogalvanic effect in SiGe quantum wells under terahertz laser irradiation, revealing how built-in asymmetry induces spin-dependent photocurrents useful for probing quantum well symmetry.

Contribution

It demonstrates that CPGE in SiGe quantum wells arises from structural asymmetry and spin splitting, providing a new method to analyze quantum well symmetry and spin-orbit interactions.

Findings

CPGE occurs due to built-in asymmetry in quantum wells.

Photocurrent is caused by optical spin orientation of carriers.

Effect can probe in-plane symmetry and spin-orbit terms.

Abstract

A detailed study of the circular photogalvanic effect (CPGE) in SiGe structures is presented. It is shown that the CPGE becomes possible due to the built-in asymmetry of quantum wells (QWs) in compositionally stepped samples and in asymmetrically doped structures. The photocurrent arises due to optical spin orientation of free carriers in QWs with spin splitting in k-space. It is shown that the effect can be applied to probe the macroscopic in-plane symmetry of low dimensional structures and allowing to conclude on Rashba or Dresselhaus terms in the Hamiltonian.