Circular photogalvanic effect due to quantum interference in the terahertz radiation absorption

We report on the observation of the circular (radiation helicity dependent) and linear photogalvanic effects in MOSFETs with n-type inversion channels fabricated on vicinal silicon surfaces. The photocurrents are excited in unbiased transistors across the source and drain contacts by terahertz radiation at normal incident. We developed the miscroscopic theory of the circular photogalvanic effect demonstrating that the helicity-dependent photocurrent in silicon structures is of pure orbital nature originating from the quantum interference of different pathways contributing to the free carrier (Drude-like) radiation absorption.