Photovoltaic effects of the GaAs (110) substrate and GaAs/AlGaAs core–shell nanowires

A semiconductor with a polar crystal symmetry can exhibit the bulk photovoltaic (BPV) effect, which can generate a photocurrent and photovoltage without requiring an interface, such as a p–n junction or Schottky barrier. GaAs, which exhibits a zinc blende lattice, displays polarity along specific crystallographic directions. In this study, we demonstrate the BPV effects of GaAs wafers oriented along the [001], [−111], and [−110] directions, in addition to those of epitaxial GaAs/Al0.2Ga0.8As core–shell nanowires (NWs) grown along the [111] direction. Local photoexcitation and the excitation-power dependence indicate that the observed photocurrent originates from the shift current mechanism. Remarkably, the grown NWs, even with sub-micron active volumes, could generate short-circuit current densities and open-circuit voltage of several mA/cm2 and several hundreds of mV, respectively, under white light illumination. These findings expand the range of BPV materials and offer orientation-engineering strategies for use in developing interface-free photovoltaic devices.