Nanostructured surfaces

Photoluminescence of γ-irradiated single-layer uncapped quantum dots
O.Strilchuk, V.Maslov, G.Rudko, E.Gule

Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, prospect Nauki 41, 03028 Kiev, Ukraine
E-mail: strilchuk@isp.kiev.ua

We report the effect of γ-irradiation on the spectral characteristics (intensity, half-width and peak position) of uncapped InxGa1-xAs/GaAs (8 ML, x = 0.4) quantum dots (QDs) grown on GaAs (100) substrate. The radiation doses varied from 1×105 to 1×108 rad. The distribution of QDs in non-irradiated sample is single-mode, and in the spectrum consists of a single wideband, which is well described by a single Gaussian.
Irradiation with low doses of γ-quanta (105 rad) improves the QDs luminescence intensity and causes the red shift of the PL band(≈70 meV). Increasing the radiation dose to 1 × 107 rad leads to PL intensity decreasing and blue-shift of luminescence band. Increase of PL intensity at low irradiation dose can be attributed to low-dose effect [1], i.e., to the improvement of crystalline quality of the irradiated sample. The red shift of PL maximum in this case is due to the changes in elastic stresses (reduction of compression stresses) [2,3]. Increasing the radiation dose to 1 × 107 rad leads to the formation of new radiation defects near/at the interfaces, which contributes to the increase of internal mechanical stresses in the quantum structure and the blue shift of PL maximum. Obviously, these defects are the centers of nonradiative recombination, which is the reason for the decrease in the QDs PL intensity

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