Hot Carrier Trapping in InAs Nanowires for Ultraviolet to Infrared Photodetection.

Semiconducting InAs nanowires are promising building blocks for optoelectronics, but their performance is often complicated by an unusual negative photoconductivity (NPC) originating from surface charge traps. Harnessing the competition between this NPC and conventional positive photoconductivity (PPC) is key to unlocking novel device functionalities. Here, we systematically investigate and control the photoresponse of InAs nanowire transistors by varying the excitation wavelength, intensity, and nanowire diameter. We demonstrate precise, wavelength-controlled switching between a strong NPC, achieving a giant negative responsivity of ∼-8.9 × 103 AW-1 under UV light, and conventional PPC in the near-infrared. To explain this competing behavior, we employ a quantitative model based on hot-carrier trapping dynamics. The model reveals that the characteristic effective trap-filling time can be tuned by over three orders of magnitude by changing the excitation wavelength from UV to near-infrared, providing a simple but powerful mechanism to control charge trapping. This work provides a predictive framework for the rational design of advanced InAs nanowire devices, including high-performance photodetectors, optical memory, and neuromorphic optoelectronics.