Broadband, Gate-Tunable, and Low-Energy-Consumption Avalanche Photodetector Based on WS₂/Ge Heterostructure

The novel broadband avalanche photodetectors based on 2-D/3-D van der Waals (vdWs) heterostructures provide a new approach for next-generation photoelectric devices. Herein, an avalanche photodetector based on WS2/Ge heterojunction with a top gate is readily realized. The ultralow dark current (
$1 \times 10^{-{10}}$
A) is obtained in the device under a gate voltage of -1 V. The photovoltaic effect allows the device to operate under zero bias with considerable responsivity (0.36/0.009 A/W) and detectivity (
$8.2 \times 10^{{11}}$
/
$2.06 \times 10^{{10}}$
jones) at 532/1550 nm. The carrier multiplication caused by avalanche breakdown in the device is also observed, resulting in the high responsivity of 92 and 3.4 A/W and the maximum gain of 6 and 175 under 532 and 1550 nm illumination, respectively. Based on the ultralow dark current and the breakdown voltage (5.0 V), as well as the broad detection region covering the visible and near-infrared range, the WS2/Ge broadband avalanche photodetector is promising for the broadband and low-energy-consumption detector applied in optical communication and laser radar imaging.