Strategy for Addressing the Low Quantum Efficiency of Nanowire Photodetectors

Nanowire photodetectors are attractive for their high speed and responsivity, enabled by small junction capacitance and high internal gain. However, their effectiveness is hampered by a low quantum efficiency due to poor light coupling to their intrinsically small size. The optically sensitive area can be increased by connecting arrays of standing nanowires (pillars) in parallel under a single readout, but the increase in dark current and total capacitance might reduce pixel sensitivity. The net effect has not yet been thoroughly investigated. In this work, we prove that such multipillar architecture indeed improves effective pixel sensitivity without reducing speed. Our theoretical analysis reveals that the pixel response time is dominated by the constituent nanowires rather than by the global capacitance, resulting in improved quantum efficiency for equivalent speed. We simultaneously characterize different pixel designs on a single focal plane array, demonstrating the viability of multipillar architectures for large-area detectors and imagers.