Freestanding single-crystalline nanomembranes and their assembly have broad application potential in photodetectors for integrated chips. However, the release and self-assembly process of single-crystalline semiconductor nanomembranes still remains a great challenge in on-chip processing and functional integration, and photodetectors based on nanomembrane always suffer from limited absorption of nanoscale thickness. Here, a non-destructive releasing and rolling process is employed to prepare tubular photodetectors based on freestanding single-crystalline Si nanomembranes. Spontaneous release and self-assembly are achieved by residual strain introduced by lattice mismatch at the epitaxial interface of Si and Ge, and the intrinsic stress and strain distributions in self-rolled-up Si nanomembranes are analyzed experimentally and computationally. The advantages of light trapping and wide-angle optical coupling are realized by tubular geometry. This Si microtube device achieves reliable Ohmic contact and exhibits a photoresponsivity of over 330 mA W-1 , a response time of 370 µs, and a light incident detection angle range of over 120°. Furthermore, the microtubular structure shows a distinct polarization angle-dependent light absorption, with a dichroic ratio of 1.24 achieved at 940 nm. The proposed Si-based microtubes provide new possibilities for the construction of multifunctional chips for integrated circuit ecosystems in the More than Moore era.
Keywords: photodetectors; polarization-sensitivity; self-rolled-up microtubes; single-crystalline Si nanomembranes.
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