Resonant circular photogalvanic effect in GaN/AlGaN heterojunctions

TL;DR

This paper reports the observation of a resonant circular photogalvanic effect in GaN/AlGaN heterojunctions, where infrared radiation induces a current that depends on photon helicity and energy, revealing a new photoelectric phenomenon.

Contribution

It demonstrates the resonant circular photogalvanic effect in GaN/AlGaN heterostructures and shows control of the current direction via photon energy tuning, a novel finding in this material system.

Findings

Current reverses with radiation helicity change.

Current direction varies with photon energy sweeping.

Resonance condition aligns with theoretical predictions.

Abstract

The resonant circular photogalvanic effect is observed in wurtzite (0001)-oriented GaN low-dimensional structures excited by infrared radiation. The current is induced by angular momentum transfer of photons to the photoexcited electrons at resonant inter-subband optical transitions in a GaN/AlGaN heterojunction. The signal reverses upon the reversal of the radiation helicity or, at fixed helicity, when the propagation direction of the photons is reversed. Making use of the tunability of the free-electron laser FELIX we demonstrate that the current direction changes by sweeping the photon energy through the intersubband resonance condition, in agreement with theoretical considerations.