Evidence for quantum-confined Stark effect in GaN/AlN quantum dots in nanowires

Semiconductor nanowires have the potential to outperform two-dimensional structures, for instance for light-emitting applications. However, the intrinsic fundamental properties of heterostructures in nanowires still remain to be assessed and compared to their two-dimensional counterparts. We show that polar GaN/AlN axial heterostructures in nanowires grown by plasma-assisted molecular-beam epitaxy are subject to a clear quantum-confined Stark effect. However, the magnitude of this effect is smaller than for two-dimensional structures due to the reduction in piezoelectric polarization that occurs thanks to elastic relaxation which is favored by the nanowire free surfaces. Moreover, we show by temperature-dependent photoluminescence measurement and single-photon correlation measurements that these heterostructures behave like quantum dots.