Extremely low inhomogeneous broadening of exciton lines in shallow (In,Ga)As/GaAs quantum wells

TL;DR

This study measures extremely narrow exciton resonance linewidths in shallow (In,Ga)As/GaAs quantum wells, revealing minimal inhomogeneous broadening and weak dependence on indium concentration and well thickness, with implications for optoelectronic applications.

Contribution

It provides the first detailed measurement of radiative linewidths in shallow quantum wells, demonstrating record narrow linewidths and the dominance of radiative effects over inhomogeneous broadening.

Findings

Record linewidths of 130-180 μeV in single quantum wells.

Non-radiative linewidth can be comparable or less than radiative linewidth.

In multilayer structures, radiative linewidth exceeds inhomogeneous broadening by four times.

Abstract

We study radiative linewidth of exciton resonance in shallow In$_x$Ga$_{1-x}$As/GaAs single quantum wells as a function of indium concentration in the range $x=0.02...0.10$ and well thickness in the range $L_Z=1...30$ nm using the method of Brewster reflection spectroscopy. Record linewidths of heavy-hole exciton resonance of about 130...180 $\mu$eV are measured in reflection spectra for single quantum wells with $L_Z=2$ nm and $x=0.02$ at temperature 9 K. In these spectra, the non-radiative linewidth including inhomogeneous broadening can be comparable or even less than radiative linewidth. It is shown that radiative linewidth weakly depends on $x$ and $L_Z$ in these ranges. In multiple-quantum-well Bragg structure with ten periods radiative linewidth exceeds inhomogeneous broadening by 4 times.