Abstract Body: InGaAs is an ideal material for near-infrared (near-IR) photodetection at telecommunications wavelengths. Its direct band gap offers strong absorption and is tunable by varying the alloy composition, making InGaAs versatile for such applications. However, most commercial devices based on this material require InP substrates, which are costly and difficult to process. Moreover, the In content of the InGaAs layer is limited by the requirement for lattice matching.[1] Nanowires are a promising avenue for heteroepitaxy of InGaAs and InAs on common substrates like Si and GaAs, and offer several performance advantages over bulk devices.[2] For example, their thin, anisotropic geometry enables devices to benefit from fast carrier collection and polarization-dependent absorption, making them suitable for fast and efficient multiplexed applications.[3] Nanowires also allow for a significant reduction in the amount of scarce materials, such as In, required to make a device. Typically, nanowires are grown vertically, perpendicular to the substrate, but vertical nanowires are notoriously difficult to incorporate into devices, and a horizontal configuration is often preferred. Recently, horizontal networks of high-quality In(Ga)As nanowires have been demonstrated by growing them on top of GaAs nanomembrane buffers using selective-area epitaxy on III-V substrates.[4,5] In this work we investigate the growth of horizontal In(Ga)As nanowire networks on GaAs substrates by molecular beam epitaxy. An epitaxial GaAs buffer nanomembrane is grown on the substrate to ensure high crystal quality In(Ga)As. Different crystallographic orientations are investigated. For growth on (111)B GaAs substrates, we demonstrate InGaAs nanowire networks positioned atop high aspect ratio GaAs nanomembranes. We show that the In content of the nanowires can be tuned up to 50% of the group III component by controlling growth conditions, but that pure InAs nanowires are not achievable.[6] Next, we demonstrate InAs nanowires grown on low-aspect ratio GaAs nanomembrane on (100) GaAs substrates. The nanowires grow conformally on the nanomembranes, which are dominated by (111) facets, and pure InAs can be achieved with just a narrow intermixed region near the interface. We compare the nanowires on each of these crystallographic orientations, highlighting their advantages for different applications. Finally, we present preliminary electrical characterization data from basic photodetector devices based on these nanowires. We compare nanowires of different lengths and widths and characterize the photoconductive response for both single nanowires and ensembles in an array. Insights from these preliminary results will guide design choices for future photodetector architectures based on these nanowires. 1 R. LaPierre et al., J. Phys. D: Appl. Phys. 50 (2017) 2 C. L. Tan et al., Nanophotonics. 7 (2018) 3 A. Dorodnyy et al., IEEE J. Sel. Top. Quant. Electr. 24 (2018) 4 M. Friedl et al., Nano Lett. 18 (2018) 5 F. Krizek et al., Phys. Rev. Mat. 2 (2018) 6 M. Friedl et al., Nano Lett. 20 (2020) Funding from Swiss National Science Foundation, NCCR QSIT

Scalable III-V Nanowire Networks for IR Photodetection

(EMC) B: Low-Dimensional Structures I

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Scalable III-V Nanowire Networks for IR Photodetection

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