Photovoltaic properties of GaAsP core-shell nanowires on Si(001) substrate

摘要

We report on the growth and electro-optical studies of photovoltaic properties of GaAsP nanowires. Low density GaAsP nanowires were grown by Auassisted MOVPE on Si(001) substrates using a two step procedure to form a radial pn junction. The STEM analyses show that the nanowires have cubic structure with the alloy composition GaAs _(0.88)P _(0.12) in the nanowire core and GaAs _(0.76)P _(0.24) in the shell. The nanowire ensembles were processed in the form of sub-millimeter size mesas. The photovoltaic properties were characterized by optical beam induced current (OBIC) and electronic beam induced current (EBIC) maps. Both OBIC and EBIC maps show that the photovoltage is generated by the nanowires; however, a strong signal variation from wire to wire is observed. Only one out of six connected nanowires produce a measurable signal. These strong fluctuations can be tentatively explained by the variation of the resistance of the nanowire-to-substrate connection, which is highly sensitive to the quality of the SiGaAsP interface. This study demonstrates the importance of the spatially resolved charge collection microscopy techniques for the diagnosis of failures in nanowire photovoltaic devices.