Tuning the luminescence emission of {105}-faceted Ge QDs superlattice using proton implantation and thermal annealing

We report on the low temperature PL emission of self-assembled Ge/Si(001) hut cluster multilayers grown by molecular beam epitaxy at relatively low temperature. We found that PL spectrum of Ge/Si hut cluster superlattice is slightly blueshifted with respect to the emission of single layer. The dependence of PL spectra on rapid thermal annealing temperature was investigated. We found a hitherto unexpected result, namely a remarkable difference in PL emission thermal behavior between multilayers and single layer. In contrast to single layer case, annealing-enhanced PL intensity is found to be ineffective for multilayer structures. Moreover, an anomalous redshift is observed after annealing below 780 °C. The origin of this redshift is tentatively attributed to a possible enhancement of the tensile strain in Si interlayers during annealing in this range of temperature. Further increase in temperature induces a blueshift in PL emission. Post-annealing induced increase of PL intensity has been found to be less pronounced than in single layer samples. We also show that proton implantation can be used to tune the emission energy of hut cluster superlattice. PL spectra are found to shift upwards depending on ion dose by ~ 25 to 130 meV after implantation followed by a flash annealing at 750 to 900 °C. The detected blueshift is attributed to radiation defect mediated Si-Ge intermixing.