  The effect of irradiation by 30-keV Ga+ and 35-keV He+ ions (in relatively
small doses) on the excitonic reflectivity spectra of single InGaAs/GaAs
quantum-well structures is studied. It is found that the irradiation results in
decreasing intensity and broadening of the excitonic resonances in the
reflectivity spectra for all the doses. It is shown that these changes are not
related to a decrease of the exciton transition oscillator strength and,
therefore, to the irradiation-induced destruction of the excitonic states, but
can be rather ascribed to a common cause, namely, to inhomogeneous broadening
of the excitonic resonances proportional to the exposure dose.A tentative model
of the irradiation-induced broadening is considered, with the mechanism of the
process being a consequence of scat-tering of the 2D excitons by structural
defects associated with Ga(In) and As vacancies arising upon collisions of the
high-energy ions with regular atoms of the crystal structure. The model is used
to compare experimental dependence of efficiency of the Ga+-ion-induced
broad-ening on distance of the quantum well from the irradiated surface with a
similar dependence calculated using the Monte-Carlo technique. A discrepancy
between the results of simulation and experimental data is discussed.

Mesoscale and Nanoscale Physics