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

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 $x=\mathrm{0.02...0.10}$ and well thickness in the range $L_Z=\mathrm{1...30}$ 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.

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