Modification of the Morphology and Light-Emitting Properties of InGaAs/GaAs Uncapped Quantum Dots by γ-Irradiation

The influence of $\gamma $ -irradiation on the morphology and light-emitting characteristics (intensity, peak position, and half-width of photoluminescence (PL) bands) of uncapped In_xGa_1-xAs/GaAs quantum dots (QDs) grown on GaAs (100) substrates is studied. The radiation doses varied in the 1– $10^{3}$ kGy range. It is found that the average size of QDs increases and the surface density of QDs decreases as the radiation dose rises. Irradiation with low doses of $\gamma $ -quanta improves the luminescence intensity of the samples due to the low-dose effect. Intensity increase at higher-dose irradiation is explained by enhancing transfer of carriers from the wetting layer (WL) to QDs via radiation-induced defect levels. The spectral position of QDs luminescence band remains unaltered or weakly blue-shifts under irradiation that is explained by the counter-play of two effects: growth of the average sizes of QDs and out-diffusion of indium from QDs.