Alternation of band gap and localization of excitons in InGaNAs nanostructures with lownitrogen content

Abstract

Continuous wave photoluminescence (cw PL) spectroscopy has been used to study theoptical properties of a set of InGaNAs epilayers and single quantum wells with nitrogenconcentration less than a few per cent at different temperatures and different excitationpowers. We found that nitrogen has a critical role on the emission light of InGaNAsnanostructures and the recombination mechanism. The incorporation of a few per cent ofnitrogen leads to shrinkage of the InGaNAs band gap. The physical origin of such band gapreduction has been investigated both experimentally and theoretically by using a bandanticrossing model. We have found that localization of excitons that have been caused byincorporation of a few per cent of nitrogen in these structures is the main explanation ofsuch anomalous behavior observed in the low-temperature photoluminescencespectra of these nanostructures. The localization energies of carriers have beenevaluated by studying the variation of the quantum well (QW) emission versustemperature, and it was found that the localization energy increases with increasingnitrogen composition. Our data also show that, with increasing excitation intensity,the PL peak position moves to higher energies (blue shift) due to the filling oflocalized states and capture centers for excitons by photo-generated carriers.