Fig. 1

Schematic sketch of nanowires (NWs) with embedded IFGARD nanodiscs with AlN barriers of 1 nm (a) and 4 nm (b) thickness. NWs with an increased barrier thickness are accompanied by an increased taper angle α due to lateral growth of the barrier material. Red + and blue - signs mark the positions of interface charges induced by the wurtzite crystal polarization. Due to the taper angle α of the NWs (b), the individual net interface charges of each AlN-barrier interface differ. In c, a sketch of the black IFGARD band profile is compared to the corresponding conventional nanodisc band profile in red. d shows HAADF-STEM images of the stacked GaN/AlN nanodiscs with 1 nm (left) and 6 nm barriers (right)