Abstract

The original work of Brunner et at.¹ and Gammon et al.² has shown that strong interface disorder in narrow quantum wells leads to strong exciton localization and confinement. The latter experiments are performed in single quantum wells covered with a thin aluminum film and processed to produce submicron sized holes. PL and PLE data show the existence of narrow single exciton-like likes lines shifted by the confinement energy as well as the presence of excited states characteristic of the energy levels produced by confinement. The typical PL spectrum obtained from a 1.5-μm-sized aperture over a 42-Å single GaAs quantum well (250- Å Ga_0.3Al_0.7As barriers) shows sharp resonances characteristic of the strong disorder that results under growth conditions with long growth interruptions producing lateral confinement comparable to the exciton Bohr radius. The spectrum shows sharp excitonic features at two locations differing by one atomic monolayer. Coherent nonlinear laser spectroscopy provides the means to obtain extensive new insight into the fundamental physical behavior of these systems but is clearly challenging because of the low signal to noise and the presence of nonresonant background nonlinearities.

© 1997 Optical Society of America