Phys.org May 10, 2023
Topological semimetals have advantages in achieving highly sensitive, low energy photodetection with ultrafast operation. Although various semimetals have been explored recently, new semimetals are still being pursued for high-responsivity photodetectors with broadband response. Researchers in China reported a pressure-induced semiconductor–semimetal transition in two-dimensional wide-band semiconducting lead iodide (PbI2). The photocurrent under visible light showed abrupt increases by two orders of magnitude at ≈25 GPa, where the crystalline structure transforms from the Pnma to I4/MMM phase. The responding band expanded from visible light to at least the telecom wavelength 1550 nm. The spectra of PbI2 suggested that the electrical band is closed at the transition point, while the charge transport showed that the sample is still not metallic. They attributed the photocurrent spurt and infrared band response to the appearance of a semimetal phase at high pressure, which explained the nonmetallic transport. The prominent drop in lifetime to a few picoseconds in ultrafast spectroscopy under pressure further confirmed the semiconductor–semimetal transition in PbI2. According to the researchers pressure-induced semi metallization opens a new strategy for designing a high-performance photodetector with broadband response… read more. TECHNICAL ARTICLE
Photocurrent of PbI2 under visible light. Credit: Cheng Peng