Group-IV Asymmetric Kagome Lattice Optical Metasurfaces

Sn-containing group-IV semiconductor nanowire (NW) alloys enhance light absorption and emission in the extended short-wave infrared (ESWIR), which is crucial to implement Si-compatible, high-performance sensing and imaging technologies [1]. Herein, we demonstrate the design, fabrication, and spectroscopic characterization of an all-dielectric multi-quantum wells (MQWs), bottom-up NW metasurface enabling light emission control at ESWIR frequencies. The platform consists of a two-dimensional Ge/[Ge_1-xSn_x/Si_yGe_1-y-zSn_z]_m core/multishell nanowire array, where m denotes the repetition period. In this work, the period was varied from 1 to 5. The vapor-liquid-solid growth of Au-catalyzed MQWs arrays is performed in a low-pressure chemical vapor deposition (CVD) reactor using germane (GeH₄), tin-tetrachloride (SnCl₄), and disilane (Si₂H₆). The fabrication of Au-patterns involves two steps: an electron beam lithography step to pattern the asymmetric Kagome layout, and an e-beam evaporation for Au deposition, followed up by Au lift-out to obtain the final Au arrays. Detailed structural characterization of the MQWs using high-resolution transmission electron microscopy images (HRTEM), combined with energy dispersive X-ray spectroscopy (EDX) revealed Si and Sn contents of 6 at.% and 4 at.%, respectively. Subsequently, low-temperature infrared photoluminescence spectroscopy is employed to quantify light emission characteristics in the designed metasurfaces. Interestingly, sharp resonances were observed near 2.1 µm with a full-width half-maximum of approximately 60 meV at 80K. Finite-difference time domain simulations were used to understand the physical mechanisms responsible for these resonances. Such metasurfaces pave the way toward efficient and Si-compatible sensing platforms in the ESWIR spectral range.
Acknowledgement: “This work is supported by the U.S. Department of Energy, under Award No. DEAC02-76SF00515, FWP100786, and Award No. DE-SC0023412, SubAward No. UA2023-351. This research is also supported by the U.S. National Science Foundation, Grant No. DMR-2003266.”
References:
[1] A. Attiaoui, et al. Advanced Materials. 35, 2300595 (2023)