High-performance unbiased Ge metal-semiconductor-metal photodetector covered with asymmetric HfSe₂ contact geometries

A Ge metal-semiconductor-metal photodetector covered with asymmetric HfSe₂ contact geometries has been proposed to realize high-performance unbiased photodetection at 1550 nm. At -1 V bias, the responsivity of this device shows a 71% improvement compared to the device without HfSe₂. Moreover, the responsivity and detectivity of this device at zero bias can reach to 71.2 mA/W and 3.27×10¹⁰ Jones, respectively. Furthermore, the fall time of this device is 2.2 µs and 53% shorter than the device without HfSe₂. This work provides a feasible way to develop unbiased Ge-based photodetectors in the near-IR communications band.