Reduced Stark shift in three-dimensionally confined GaN/AlGaN asymmetric multi-quantum disks

The optical transitions of the three-dimensionally confined GaN/AlGaN asymmetric multi quantum disks were characterized by micro photoluminescence and time-resolved photoluminescence. Several fine emission lines, originating from the wide and narrow quantum disks, were observed around 3.7 eV from a single nanocolumn dispersed on a patterned SiO2 substrate. The photoluminescence from the wide quantum disk shifts a little with increasing excitation power, while that from the narrow quantum disk does not shift. This effect can be explained by carrier tunneling for the 3-dimensionally confined quantum disks. Kelvin probe force microscopy results confirm that the GaN/AlGaN multiquantum disks are surrounded by a GaN shell, which has a higher potential than core GaN.