Spatially-resolved optical studies on intermixing of InGaAs quantum-dot laser structures by using an AIAs native oxide and thermal annealing

We have studied the optical properties of InGaAs quantum dot (QD) laser structures with Al oxide (AlO _x) as a current-blocking layer by means of photoluminescence (PL) and spatially-resolved micro-PL techniques. A dominant, broad PL emission due to the intermixing effect of the AlO _x layer was observed at a PL emission energy higher than that of the non-intermixed region. To characterize the optical properties of the intermixed and the non-intermixed regions of InGaAs QDs, we performed low-temperature (77 K) micro-PL experiments. We observed InGaAs QD emission at about 1.1 eV in the non-oxide AlAs region while the PL emission energy for the AlO _x layer region was shifted to about 1.16 eV. For the reference sample without heat, treatment, only a PL emission at about 1.1 eV was observed. We conclude that the intermixing effect of the InGaAs QD region under an AlO _x layer is stronger than that of the InGaAs QD region under a non-oxided AlAs layer.