Field-Effect Persistent Photoconductivity

TL;DR

This paper demonstrates how illumination and gate bias can control the persistent photoconductivity in AlAs and GaAs quantum wells, with the effect depending on the Al composition in the barriers.

Contribution

It introduces a method to tune two-dimensional electron density in quantum wells via combined illumination and gate bias at low temperatures, highlighting the role of barrier composition.

Findings

Persistent photoconductivity can increase or decrease electron density.

Control of carrier density is achieved by tuning gate bias during illumination.

The effect is maximized at a specific Al mole fraction in the barrier.

Abstract

We report a persistent increase or decrease in the two-dimensional electron density of AlAs or GaAs quantum wells flanked by AlGaAs barriers, brought about by illuminating the samples at T ~ 4 K while simultaneously applying a voltage bias between a back gate and the two-dimensional electron gas. Control of the final carrier density is achieved by tuning the back gate bias during illumination. Furthermore, the strength of the persistent photoconductivity depends on the Al mole fraction in the back Al_{x}Ga_{1-x}As barrier, and is largest at $x \simeq 0.4$.