Engineering light absorption in the extended short-wave infrared (e-SWIR) range using scalable materials is a long-sought-after capability that is crucial to implement cost-effective and highperformance sensing and imaging technologies. Herein, we demonstrate enhanced, tunable e-SWIR absorption using silicon-integrated platforms consisting of ordered arrays of metastable GeSn nanowires with Sn content reaching 9 at.% and variable diameters. Detailed simulations were combined with experimental analyses to systematically investigate light-GeSn nanowire interactions to tailor and optimize the nanowire array geometrical parameters and the corresponding optical response. The diameter-dependent leaky mode resonance peaks are theoretically predicted and experimentally confirmed with a tunable wavelength from 1.5 to 2.2 μm. A three-fold enhancement in the absorption with respect to GeSn layers at 2.1 µm was achieved using nanowires with a diameter of 325 nm. Finite difference time domain simulations unraveled the underlying mechanisms of the e-SWIR enhanced absorption. Coupling of the HE11 and HE12 resonant modes to nanowires is observed at diameters above 325 nm, while at smaller diameters and longer wavelengths the HE11 mode is guided into the underlying Ge layer. The presence of tapering in NWs further extends the absorption range while minimizing reflection. This ability to engineer and enhance e-SWIR absorption lays the groundwork to implement novel photonic devices exploiting all-group IV platforms.
Group IV Ge1–x Sn x semiconductors hold the premise of enabling broadband silicon-integrated infrared optoelectronics due to their tunable band gap energy and directness. Herein, we exploit these attributes along with the enhanced lattice strain relaxation in Ge/Ge0.92Sn0.08 core/shell nanowire heterostructures to implement highly responsive room-temperature short-wave infrared nanoscale photodetectors. Atomic-level studies confirm the uniform shell composition and its higher crystallinity with respect to thin films counterparts. The demonstrated Ge/Ge0.92Sn0.08 p-type field-effect nanowire transistors exhibit superior optoelectronic properties achieving simultaneously relatively high mobility, high ON/OFF ratio, and high responsivity, in addition to a broadband absorption in the short-wave infrared range. Indeed, the reduced band gap of the Ge0.92Sn0.08 shell yields an extended cutoff wavelength of 2.1 μm, with a room-temperature responsivity reaching 2.7 A/W at 1550 nm. These results highlight the potential of Ge/Ge1–x Sn x core/shell nanowires as silicon-compatible building blocks for nanoscale-integrated infrared photonics.
The hole mobility of two-dimensional (2D) gas at (001) and (111) diamond/insulator interfaces is investigated theoretically and compared with experimental data from the literature. It is shown that the surface impurity scattering is the limiting mechanism at room temperature in most of the H-terminated diamond field effect transistors, where the negative charges created by transfer doping are in the vicinity of the 2D gas. By repelling the negative charges at the metal/insulator interface, as recently reported for the (111) h-BN/diamond interface, we demonstrate that it is possible to achieve high mobility values of the order of 3000 cm2/V s when a pure phonon scattering occurs. This work confirms the potential of two-dimensional hole gas diamond field effect transistors for high power and high frequency applications.
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