Abstract
Recent advances in nanoscale optoelectronic Ge devices have exposed their enormous potential for highly sensitive visible and near-infrared CMOS compatible photodetectors. In this respect, Ge nanowires, due to their nanocylinder resonator shape, have established themselves as a promising platform to significantly enhance the performance of photodetectors. Here, we present a highly sensitive polarity switchable Ge nanowire photodetector embedded in a monolithic and single-crystalline metal–semiconductor nanowire heterostructure. Operated in the negative differential resistance regime, effective dark current suppression up to a factor of 100 is achieved. In this configuration, a bias-switchable positive and negative photoconductance is observed and systematically analyzed. Further, a remarkably strong polarization anisotropy with a maximum TM/TE ratio of 33 was found for positive photoconductance. Most notably, presenting a Ge-based photodetector combining switchable photoconductance and effective dark current suppression may pave the way for advanced applications, including highly resolved imaging and light effect transistors.
Highlights
Recent advances in nanoscale optoelectronic Ge devices have exposed their enormous potential for highly sensitive visible and near-infrared CMOS compatible photodetectors
We demonstrate a highly sensitive Ge NW photodetector with switchable photoconductance, effective dark current suppression, and polarization sensitivity
Operation (Figure 2): While the negative photoconductance (NPC) is a result of the photogating effect, that is, excited electrons are efficiently trapped, acting as negative local gate, the valley region of the negative differential resistance (NDR) enables a significant drop of IDark, below the current under illumination resulting in a positive photoconductance (PPC)
Summary
Recent advances in nanoscale optoelectronic Ge devices have exposed their enormous potential for highly sensitive visible and near-infrared CMOS compatible photodetectors. To probe the dark-characteristic of our Al−Ge−Al-based photodetector, we applied a bias to the highly p-doped Si substrate, operating the device as a back-gated field-effect transistor (FET).
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