Polarization dependence study of electroluminescence and absorption from InAs/GaAs columnar quantum dots

Semiconductor optical amplifiers based on InGaAs columnar quantum dots (CQDs) with different numbers of superlattice periods were fabricated and tested. The polarization dependence of the electroluminescence (EL) and absorption of such CQDs structures were measured. Compared to standard QDs a large improvement in the ratio of transverse-magnetic (TM) and -electric (TE) integrated EL was obtained in CQDs, depending on the number of stacked GaAs/InAs superlattice periods, which can be attributed to the more symmetric shape of CQDs. TM and TE resolved photovoltage absorption spectroscopy confirmed this improvement. A small spectral separation between TE- and TM-EL peaks has been observed showing that heavy and light holelike states are energetically close in these QDs.