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Here, we presented a novel near-infrared (NIR) photodetectors based on Si micro-holes array/graphene (SiMHs/Gr) Schottky barrier diode (SBD) for monitoring heart rate. The SBD exhibited a unique self-filtered NIR response in a range from 900 nm to 1160 nm with a responsivity of 122 mA/W at zero bias voltage. Moreover, our device possessed an ultrahigh signal to noise ratio (SNR) of more than $10^{{5}}$ between visible and NIR light. The presented self-filtered NIR photodetector was used as a non-contact transmission-type photoplethysmography sensor for real-time heart rate monitoring. Due to the suppression of disturbances caused by ambient light, our device performed more accurate heart rate monitoring than those extracted from commercial broadband photodetectors. [ABSTRACT FROM AUTHOR]

A high Schottky barrier height (ΦB) is one of the essential prerequisites for achieving high‐performance self‐powered Schottky‐barrier diode (SBD)‐based photodetector. The ΦB value is predominantly determined by the metal function and interface quality of the metal/semiconductor contact. 2D MXenes with adjustable work functions and dangling bond‐free properties are promising building blocks for constructing self‐powered SBD with high ΦB. Herein, a novel Ti3C2Tx MXene/Si hexagonal microhole array (SiHMA) van der Waals SBD is developed for the first time via a feasible solution process. Significantly, the device possesses a large ΦB up to ≈1.07 eV, which is among the highest for the Si‐based SBD. In consequence, the Ti3C2Tx/SiHMA SBD yields a large responsivity up to 302 mA W−1 and detectivity as high as 5.4 × 1013 Jones in a self‐powered model, surpassing the performance of most 2D material/Si photodiodes reported to date. Furthermore, it is demonstrated that featured and reliable fingertip photoplethysmogram (PPG) signals can be detected using the self‐powered SBD, enabling us to further accurately extract the heart rate (HR), and blood pressures (BP) using the PPG‐only method. This work paves the way for the construction of high‐performance MXenes‐based self‐powered SBDs for health monitoring. [ABSTRACT FROM AUTHOR]

In this letter, we demonstrate the fabrication of a conformal CuO/Si microholes array heterojunction through the DC reactive magnetron sputtering from a high-purity Cu target. By using the monolayer graphene as the top electrode, the device served well as a self-powered vis-NIR photodetector, showing a high responsivity of 301.5 mA W−1, specific detectivity of $7.96\times 10^{12}$ Jones and a fast response speed (rise time $9.9~\mu $ s and fall time $10~\mu \text{s}$) upon 530 nm illumination. Compared to its planar counterpart, the responsivity was remarkably enhanced over the broadband region. The underlying reason should be ascribed to the improved light trapping in the microholes via the longitudinal Fabry-Perot (F-P) cavity resonance, according to theoretical simulation by finite-difference time-domain (FDTD) solution. Such an effect gave rise to an enhanced light-matter interaction, leading to the improved photoresponse. This work also opens up an effective way for the on-chip high performance photodetection due to the well compatibility with the current complementary metal-oxide-semiconductor (CMOS) technology. [ABSTRACT FROM AUTHOR]

Photodetectors based on high-performance, two-dimensional (2D) layered transition metal dichalcogenides (TMDCs) are limited by the synthesis of larger-area 2D TMDCs with high quality and optimized device structure. Herein, we report, for the first time, a uniform and stacked–layered MoSe2 film of high quality was deposited onto Si substrate by using the pulsed laser deposition technique, and then in situ constructed layered MoSe2/Si 2D–3D vertical heterojunction. The resultant heterojunction showed a wide near-infrared response up to 1550 nm, with both ultra-high detectivity up to 1.4 × 1014 Jones and a response speed approaching 120 ns at zero bias, which are much better than most previous 2D TMDC-based photodetectors and are comparable to that of commercial Si photodiodes. The high performance of the layered MoSe2/Si heterojunction can be attributed to be the high-quality stacked–layered MoSe2 film, the excellent rectifying behavior of the device and the n-n heterojunction structure. Moreover, the defect-enhanced near-infrared response was determined to be Se vacancies from the density functional theory (DFT) simulations. These results suggest great potential of the layered MoSe2/Si 2D–3D heterojunctions in the field of communication light detection. More importantly, the in situ grown heterojunctions are expected to boost the development of other 2D TMDCs heterojunction-based optoelectronic devices. [ABSTRACT FROM AUTHOR]

Graphical abstract A self-powered Gr/Si heterojunction was successfully fabricated by using graphene film as active area. The device exhibits a responsivity approaching 39.5 mAW−1, together with a high-speed response speed up to 5.0 μs to communication wavelength of 1.55 μm. Highlights • A self-powered Gr/Si heterojunciton photodetector was fabricated by using graphene as the active area. • The Gr/Si heterojunciton photodetector shows an excellent rectification behavior and a sensitivity to 1.55 μm IR light. • High responsivity and high speed of the Gr/Si heterojunction were achieved. • The device performance are superior to most of previous graphene-based photodetectors. Abstract Graphene has shown great potentials for new-generation photodetectors in view of its outstanding optical and electrical properties, especially its ultra-broad range absorption. Most of graphene(Gr)/Si hybrid two-dimensional(2D)-three-dimensional(3D) photodetectors, which offer a perspective on future application in integrated optoelectronics, are still however enabled the excellent detection on visible light. Herein, we reported a self-powered Gr/Si Schottky heterojunciton with a high sensivity to communication light of 1.55 μm wavelenght by using graphene film as active area. The resultant photodetectors showed a high-speed response speed up to 5.0 μs, togther with a responsivity approaching 39.5 mAW−1, which are comparable with previous graphene-based photodetectors and superior to previous Gr/Si heterojunction. The high-performance of the schottky heterojunction can be ascribed to featuring a built-in field facilitating to separate photocarriers. Combined our results with the methodology of devcie fabrication, can be utilized as pathway for large-area integration of 1.55 μm communication light photodetectors. [ABSTRACT FROM AUTHOR]