Multiphysics-Coupled Strain Engineering in Flexible 3D-Graphene/Germanium Heterostructures for Broadband Photodetection.

Ma, Hui; Yin, Ailing; Cao, Genqiang; Li, Shubo; Qian, Kuan; Zhang, Jinqiu; Lian, Shanshui; Xu, Wenwu et al. · Nano Lett · 2026

basic_science · Level V

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Abstract

Flexible photodetectors that maintain structural integrity while offering tunable photoelectric responses under deformation face challenges in material selection. Germanium (Ge) is a promising candidate for its strong absorption in the visible- to near-infrared spectrum, yet the mechanisms of interfacial modulation and photoelectric responses in ultrathin flexible germanium remain poorly understood. This study presents a 3D-graphene/Ge heterostructure on 4 in. flexible Ge thin films (∼15 μm thick). The flexible photodetector demonstrates a stable photoelectric response from 380 to 1850 nm, with a responsivity of 80.2 A W<sup>-1</sup> and a detectivity of 1.2 × 10<sup>11</sup> jones at 1850 nm. It has low noise (2.2 × 10<sup>-21</sup> A<sup>2</sup> Hz<sup>-1</sup>), rapid response times (rise/fall times of 164 and 161 μs), and a -3 dB cutoff frequency of 1.8 kHz. The device remains stable after over 10<sup>4</sup> bending cycles and dynamic deformation. Practical applications involve multispectral imaging and wearable setups for fingertip and wrist photoplethysmography-based monitoring.