Nanoscale analysis of electrical junctions in InGaP nanowires grown by template-assisted selective epitaxy

We report the analysis of the electrical properties of In_x−1Ga_xP nanowires (NWs) grown by template-assisted selective epitaxy. The individual NW properties are investigated by means of electron beam induced current microscopy (EBIC) and current-voltage curves acquired on single nano-objects. First, a set of samples containing n-doped InGaP NWs grown on a p-doped Si substrate are investigated. The electrical activity of the hetero-junction between the NWs and the substrate is demonstrated and the material parameters are analyzed, namely, the n-doping level is determined in relation to the dopant flow used during the growth. These results were used to design and elaborate InGaP NWs containing a p-n homo-junction. The electrical activity of the homo-junction is evidenced using EBIC mapping on single NWs, and material parameters (namely, the doping and the minority carrier diffusion lengths) for the p- and n-doped InGaP segments are estimated. Finally, the first proof of a photovoltaic effect from the NW homo-junctions is obtained by photocurrent measurements of a contacted NW array under white light irradiation.