Nanobowls-assisted broadband absorber for unbiased Si-based infrared photodetection

Abstract

Hot electrons from the nonradiative decay of surface plasmons have drawn extensive attention due to the outstanding performance in realizing below-bandgap photodetection. However, the widely employed metallic nanostructures are normally complex and delicate with a great challenge in large-area fabrication, and there is a great limitation to achieve substantial photoresponse at relatively long wavelengths (e.g., 2000nm) with polarization- and incident-angle independence. In this study, we theoretically and experimentally demonstrate a broadband, omnidirectional, and polarization-insensitive absorber based on wafer-scale silicon honeycomb nanobowls with 20-nm-thick gold overlayer. The average absorption across the long wave near infrared band (LW-NIR, i.e., 1100−2500 nm) is higher than 82%, which is contributed from the random nature and multimode localized plasmonic resonances excited on the side walls of nanobowls. Benefitted from the well-connected thin Au film and relatively low Schottky barrier, the generated hot electrons have a high transport probability to reach Schottky interface and participate in the interfacial charge transfer process. As a result, the hot-electron photodetector under no bias realizes a broadband photodetection up to 2000nm wavelength with a responsivity of 0.145 mA/W, and its cutoff wavelength is predicted up to 3300 nm by fitting the experimental result with Fowler theory. Our proposed Au/Si nanobowls photodetector could open a pathway to further extend the detection wavelength of Si-based photodetectors with a large-area and low-cost fabrication process, which promotes practical hot-electron applications.

Recent Progress and Future Opportunities for Hot Carrier Photodetectors: From Ultraviolet to Infrared Bands

“…[10,30,69] Therefore, the various metallic nanostructures including nanodots, antennas, metamaterials, islands, plasmonic crystals, grating, and waveguide are employed to excite SP for an improved responsivity. [6,22,24,51,57,[110][111][112][113][114][115][116][117][118][119][120][121][122][123][124][125][126][127] In general, the unbiased responsivities of the hot carrier photodetectors working at the LW-NIR are on the order of mA/W, much lower than that of the commercially available near-infrared photodetectors, e.g., indium arsenide (InAs), gallium arsenide (GaAs), and mercury cadmium telluride (HgCdTe). [112] To further improve the efficiency of hot carrier photodetectors, more works can be interesting from the following perspectives.…”

CMOS-Compatible Broad-Band Hot Carrier Photodetection with Cu–Silicon Nanojunctions

“…It is clear that the Cu–SiNH devices exhibit a higher EDOS above the Fermi level at excitation P j and higher ejection probability P e and therefore higher IQE and longer cutoff wavelength. By applying advanced interface treatment and optimized nanojunction design, the photodetection performance is expected to improve further.…”

“…However, Au and Ag are expensive and not complementary metal–oxide–semiconductor (CMOS)-compatible, which limits their wide application. The large Au–Si Schottky barrier height also limits the cutoff operating wavelength to approximately 1.6 μm in most cases, although some work claims that interface treatment cycles using oxidation and etching processes can obtain longer cutoff wavelengths . Noble metals combining a significantly high real part (negative) of permittivity and a low imaginary part are usually considered as the first choice for plasmonics due to the relatively low Ohmic loss. , Plasmonic absorption is preferred in HC harvesting unlike optoelectronic integration circuits or biosensing applications.…”

“…The large Au−Si Schottky barrier height also limits the cutoff operating wavelength to approximately 1.6 μm in most cases, although some work claims that interface treatment cycles using oxidation and etching processes can obtain longer cutoff wavelengths. 22 plasmonics due to the relatively low Ohmic loss. 28,29 Plasmonic absorption is preferred in HC harvesting unlike optoelectronic integration circuits or biosensing applications.…”

“…Gold is the most popular candidate as a plasmonic metal to construct a M–S Schottky junction to collect HCs. For example, the Au–Si Schottky junction combined with various plasmonic structures has demonstrated broad-band near-infrared (NIR) photodetection beyond the cutoff wavelength of the interband transition in silicon, ,− narrowband photodetection with a full-width at half-maximum of sub-10 nm, , circularly polarized light detection in chiral plasmonic structures, and 40 Git/s data reception using a plasmonic waveguide detector with a responsivity of 120 mA/W at 1550 nm . Silver was also used to construct a plasmon-induced sub-bandgap photodetector with organic Schottky diodes .…”