The optoelectronic performance of axial and radial GaAs nanowire pn-diodes

Axial and radial core-multi-shell GaAs nanowire pn-diodes have been fabricated via MOVPE epitaxy. Nanowire diodes show macroscopic diode-like IV-characteristics. Ultra-low reverse current giving rise to an on/off ratio of about 10⁶ was measured for axial pn-junctions. Radial nanowire-diodes demonstrated significantly higher photocurrents in comparison with axial nanowire geometry. Spatially resolved photocurrent spectroscopy was used to investigate mechanism of carrier photo generation. Optical generation of carriers at the pn-junction is shown to dominate the photo response. The fill factors of 73% for axial and 57% for radial pn-diodes were measured at room temperature under monochromatic illumination (λ = 532 nm) and scale with the illumination intensity in a wide intensity range.