LAUSR

DOI: 10.1002/adom.201900823 inspired applications such as optical resonators,[6] passive electronic components[7] microrobotics,[8] gas detection,[9] energy storage,[10] and bioplatforms.[11] Silicon photodetectors have been intensively studied due to its mass production and low cost with standard complementary metal–oxide–semiconductor (CMOS) manufacturing processes.[12] Traditional silicon nanomembrane (SiNM) detectors face the challenge of low light absorption coefficient, nonperfect response properties and angle-dependent light detection. To overcome these limitations and further promote photodetection performance, alternative materials and methodologies including graphene,[13] transitional metal dichalcogenides,[14] surface plasmon polariton[15] and quantum dot[16] have been explored as potential candidates. However, these photodetectors are often hindered by instability or high-cost and therefore unfavorable along the path to their commercialization. It is still challenging to fabricate omnidirectional all-Si photodetectors and improve its sensitivity. In this work we demonstrate that 3D silicon-based photodetectors could be fabricated by rolling up ultrathin silicon nanomembranes (SiNMs). Strain distributions within the circular structure were characterized with micro-Raman spectroscopy of different excitation lasers. The tensile strain in the functional SiNMs could be well manipulated by tuning the strain layer thickness and etching parameters during the rolled-up fabrication process. The optoelectronic performance of 3D tubular Si photodetector was also investigated, exhibiting enhanced broadband photodetection and responsivity, which resulted from increased photocurrent and suppressed dark current. Furthermore, the unique tubular structure enables omnidirectional enhanced sensitivity over a wide incident angle, even without extra light-coupling plasmonics designs or optimized doping patterns.[17] Our work paves the way for integrating 3D photodetectors with on-chip silicon circuits and opens up possibilities for design and construction of future generations of sophisticated 3D optoelectronic devices. The schematic illustration of the rolled-up Si photodetector is presented in Figure 1a. The device consists of two chromium electrodes on the 20 nm thick SiNM and a 20 μm wide Si channel. We use chromium because Cr could not only serve as the strain layer but also was found to form a perfect Schottky contact with ultrathin SiNM.[18] The Cr layer was deposited on precleaned SiNM by e-beam evaporation with Advanced 3D mesostructures have prominent applications in flexible electronics, photonics, mechanics, and biomedicine. Here, 3D tubular silicon photodetectors are demonstrated by self-rolling ultrathin silicon nanomembranes with enhanced broadband photodetection and responsivity. Strain distributions within the unique circular structures are investigated with micro-Raman spectroscopy, while the tensile strain of the rolled-up microtubes can be controlled with the tube diameter by modifying the membrane thickness and etching parameters during the rolled-up process. The tubular photodetector exhibits increased photocurrent and suppressed dark current compared with planar devices over a wide incident angle. This study provides a novel approach to construct high-performance omnidirectional Si-based photodetectors and offers promising prospects for design and manufacture of complex 3D optoelectronic devices.