We have grown GaAsP nanowires with high optical and structural quality by Aerotaxy, a new continuous gas phase mass production process to grow III-V semiconductor based nanowires. By varying the PH3/AsH3 ratio and growth temperature, size selected GaAs1-xPx nanowires (80 nm diameter) with pure zinc-blende structure and with direct band gap energies ranging from 1.42 to 1.90 eV (at 300 K), (i.e., 0 ≤ x ≤ 0.43) were grown, which is the energy range needed for creating tandem III-V solar cells on silicon. The phosphorus content in the NWs is shown to be controlled by both growth temperature and input gas phase ratio. The distribution of P in the wires is uniform over the length of the wires and among the wires. This proves the feasibility of growing GaAsP nanowires by Aerotaxy and results indicate that it is a generic process that can be applied to the growth of other III-V semiconductor based ternary nanowires.

We report gallium arsenide (GaAs) growth rates exceeding 300 µm h −1 using dynamic hydride vapor phase epitaxy. We achieved these rates by maximizing the gallium to gallium monochloride conversion efficiency, and by utilizing a mass-transport-limited growth regime with fast kinetics. We also demonstrate gallium indium phosphide growth at rates exceeding 200 µm h −1 using similar growth conditions. We grew GaAs solar cell devices by incorporating the high growth rate of GaAs and evaluated its material quality at these high rates. Solar cell growth rates ranged from 35 to 309 µm h −1 with open circuit voltages ranging from 1.04 to 1.07 V. The best devices exceeded 25% efficiency under the AM1.5 G solar spectrum. The high open-circuit voltages indicate that high material quality can be maintained at these extremely high growth rates. These results have strong implications toward lowering the deposition cost of III-V materials potentially enabling the deposition of high efficiency devices in mere seconds.

Nanowires bring new possibilities to the field of hot-carrier photovoltaics by providing flexibility in combining materials for band engineering and using nanophotonic effects to control light absorption. Previously, an open-circuit voltage beyond the Shockley–Queisser limit was demonstrated in hot-carrier devices based on InAs–InP–InAs nanowire heterostructures. However, in these first experiments, the location of light absorption, and therefore the precise mechanism of hot-carrier extraction, was uncontrolled. In this Letter, we combine plasmonic nanoantennas with InAs–InP–InAs nanowire devices to enhance light absorption within a subwavelength region near an InP energy barrier that serves as an energy filter. From photon-energy- and irradiance-dependent photocurrent and photovoltage measurements, we find that photocurrent generation is dominated by internal photoemission of nonthermalized hot electrons when the photoexcited electron energy is above the barrier and by photothermionic emission when the energy is below the barrier. We estimate that an internal quantum efficiency up to 0.5–1.2% is achieved. Insights from this study provide guidelines to improve internal quantum efficiencies based on nanowire heterostructures.

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