Optical and transport properties correlation driven by amorphous/crystalline disorder in InP nanowires

Abstract

Indium phosphide nanowires with a single crystalline zinc-blend core and polycrystalline/amorphous shell were grown from a reliable route without the use of hazardous precursors. The nanowires are composed by a crystalline core covered by a polycrystalline shell, presenting typical lengths larger than 10 μm and diameters of 80-90 nm. Raman spectra taken from as-grown nanowires exhibited asymmetric line shapes with broadening towards higher wave numbers which can be attributed to phonon localization effects. It was found that optical phonons in the nanowires are localized in regions with average size of 3 nm, which seems to have the same order of magnitude of grain sizes in the polycrystalline shell. Regardless of the fact that the nanowires exhibit a crystalline core, any considerable degree of disorder can lead to a localized behaviour of carriers. In consequence, the variable range hopping was observed as the main transport instead of the usual thermal excitation mechanisms. Furthermore the hopping length was ten times smaller than nanowire cross-sections, confirming that the nanostructures do behave as a 3D system. Accordingly, the V-shape observed in PL spectra clearly demonstrates a very strong influence of the potential fluctuations on the exciton optical recombination. Such fluctuations can still be observed at low temperature regime, confirming that the amorphous/polycrystalline shell of the nanowires affects the exciton recombination in every laser power regime tested.

Photocurrent enhancement and magnetoresistance in indium phosphide single nanowire by zinc doping

“…Semiconductor materials have been widely employed in highefficiency photosensitive systems, mainly as thin films, substrates or nanowires [1]. Most of them are composed of alloys produced by elements of the groups III−V , such as indium phosphide (InP), whose inherent presence of a direct bandgap (1.34 eV at 300 K) in the visible-near-infrared (vis-NIR) range guarantees its sensitivity to electronic excitations in the visible range of solar radiation [2]. Allied to the great values of surface-to-volume ratio at the nanometer scale, these remarkable tools are currently being investigated for employment as a new generation of photo-electronic devices [1][2][3][4][5].…”

“…In this regard, InP nanowires have been demonstrated to be a class of very promising key materials to be used in photovoltaic systems due to their high photosensitivity [2,5]. Studies on devices built from semiconductor nanowires and ferromagnetic contacts have demonstrated that both spin and charge can be explored in order to get spintronic functionalities [6].…”