Photocurrent spectroscopy of GaAs/GaP hetero-structured nanowires*

We study the photocurrent from photoexcited charge carriers in GaAs/GaP axial and radial hetero-structured nanowires (NWs). These NWs are grown using Metal-Organic Chemical Vapor Deposition (MOCVD) in [111]B direction with Au nano-particles as catalysts. As grown axial GaAs/GaP NWs are sonicated in methanol and dispersed on Si-SiO insulated substrate. Photolithography followed by Ti/Al (20nm/300nm) metal evaporation and lift-off is used to fabricate contacts in Metal-semiconductor-metal across single NW. Spatial imaging of photocurrent at different wavelengths distinguishes the GaP and GaAs regions in these NWs. Peak photocurrent is observed around GaP region for light wavelengths $\sim$ 458nm whereas peak photocurrent is shift towards GaAs region for light wavelength $\sim$ 800nm. Photocurrent measurements in GaAs/GaP strained core-shell NWs are in progress.