Theoretical and experimental investigation of III-V semiconductor nanowire heterostructures

This thesis concerns a theoretical and experimental investigation of two applications of semiconductor nanowires and nanowire heterostructures. First, the development of nanowire-planar tandem solar cells is considered from a theoretical standpoint. The maximum efficiency of the solar cell is determined in the radiative limit as a function both of the material bandgaps and the absorption efficiency of the nanowire array. This work provides design guidelines for the experimental realisation of such a solar cell. The catalyst-free growth of GaAs nanowires is then developed, with potential for future use within a nanowire solar cell. Control over radial and axial nanowire growth is demonstrated. GaAs nanowires are employed as the host for single photon emitters in the form of InGaAs nanowire quantum dots. This leverages the position control inherent in the growth technique, and represents the first realisation of individually addressable nanowire quantum dots grown by this technique. This provides a promising route for future scale up for quantum information applications. The limits of the catalyst-free growth technique are investigated, leading to the first demonstration of morphology control of a catalyst-free nanowire. Nanowires are grown with elongated cross-section, resulting in the emission of linearly polarized light from the top facet of the nanowire. Finally, the growth of InAsP nanowire quantum dots within InP nanowires is developed. Photoluminescence emission is detected at lower energy than expected for polytypic InP, demonstrating successful growth of an InAsP nanowire heterostructure.