Diffusion length measurements in axial and radial heterostructured nanowires using cathodoluminescence

We have measured the ambipolar diffusion lengths in nanowires with GaAs and AlGaAs core material using cathodoluminescence imaging. This was done by combining III–V semiconductor materials with different bandgaps in single nanowires. We show that it is possible to record intensity profiles of the emission from segments of lower bandgap material positioned along the nanowire length and in this way gain an insight on important carrier transport properties of the nanowire core material. We present diffusion data for GaAs and AlGaAs nanowire core material in different radially and axially heterostructured nanowires and show that the diffusion of carriers is greatly increased by capping the nanowires with a higher-bandgap material. In addition, we show how a decoupling of the radial and axial growth during particle-seeded growth is necessary in order to reach long diffusion lengths along the core of axially heterostructured nanowires. In addition, for ternary compounds (InGaAs and AlGaAs), we observe compositional differences for radial and axial nanowire growth.