Experimental evidences of quantum confined 2D indirect excitons in single barrier GaAs/AlAs/GaAs heterostructure using photocapacitance at room temperature

TL;DR

This study demonstrates room-temperature detection of quantum confined 2D indirect excitons in GaAs/AlAs/GaAs heterostructures using photocapacitance spectroscopy, revealing unique exciton dynamics and the technique's effectiveness for probing small exciton populations.

Contribution

It introduces photocapacitance spectroscopy as a novel method for detecting and studying indirect excitons in heterostructures at room temperature, highlighting its advantages over traditional methods.

Findings

Photocapacitance spectra show well-defined indirect exciton resonances.

Distinct exciton dynamics are observed between photocapacitance and photocurrent measurements.

Photocapacitance effectively detects small populations of indirect excitons with large dipole moments.

Abstract

We investigated excitonic absorptions in GaAs/AlAs/GaAs single barrier heterostructure using both photocapacitance and photocurrent spectroscopies at room temperature. Photocapacitance spectra show well defined resonance peak of indirect excitons formed around the Gamma-AlAs barrier. Unlike DC-photocurrent spectra, frequency dependent photocapacitance spectra interestingly red shift, sharpen up and then decrease with increasing tunneling at higher biases. Such dissimilarities clearly point out that different exciton dynamics govern these two spectral measurements. We also argue why such quantum confined dipoles of indirect excitons can have thermodynamically finite probabilities to survive even at room temperature. Finally, our observations demonstrate that photocapacitance technique, which was seldom used to detect excitons in the past, is useful for selective detection and experimental tuning of relatively small numbers (~10^11/cm2) of photo-generated indirect excitons having large effective dipole moments in this type of quasi-two dimensional heterostructures.