Enhanced Photocurrent and Suppressed Dark Current of MXene/Ge Heterostructure-Based Near-Infrared Photodetectors Enabled by Surface Charge Transfer Induced Inversion Layer

2-D MXene/narrow-gap material heterostructures represent a class of hopeful platforms for highly efficient and low-budget near-infrared (NIR) photodetection. Nonetheless, performance improvement is astricted by the comparatively low junction barrier height due to minor work function discrepancy between two components. In this work, a surface inversion layer is introduced between 2-D MXene film and n-Ge substrate exploiting a surface charge transfer doping technique. The coating of MoO3 layer with a high work function induces spontaneous electron extraction from n-Ge toward MoO3 layer. The charge transfer produces a p-type inversion layer on n-Ge surface, which markedly enhances built-in electric field and restrains photocarrier recombination. As a consequent, the optoelectronic performance of a 2-D MXene/Ge heterostructure-based NIR light detector is greatly improved. Specifically, the responsivity and specific detectivity are enhanced from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$370.9~\text {mA}\cdot \text {W}^{-{1}}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.22 \times 10^{{11}}$ </tex-math></inline-formula> Jones to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$702.5~\text {mA}\cdot \text {W}^{-{1}}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.17\times 10^{{12}}$ </tex-math></inline-formula> Jones, respectively, upon 1550-nm light illumination at self-driven working mode. Around one order of magnitude suppression in dark current is observed. In addition, the detector exhibits quick response speed of 25.2/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$31.8~\mu $ </tex-math></inline-formula>s and robust operational durability as well. The present study provides a hopeful scheme for further improving the property of 2-D material/semiconductor heterostructure-based photoelectronic devices.