III-V semiconductor nanowires possess fascinating material properties, which pave the way towards the fabrication of next-generation nanoscale electronic and optoelectronic devices. In particular, owing to their distinctive nanostructure nature, III-V nanowires exhibit unique properties that do not exist in their bulk form. Such remarkable one-dimensional geometry provides us great opportunities to leverage their surface characteristics (for example, through surface decoration or modification by a functional layer) to spark new phenomenon which is barely attainable in conventional nanowires, paving the way for developing next-generation nanoscale electronic and optoelectronic devices.
In a new paper published in Light Science & Application, a team of scientists, led by Professor Haiding Sun, School of Microelectronics at University of Science and Technology of China and co-workers have combined earth-abundant molybdenum sulfides with the popular group III-nitride semiconductor nanowires to form III-nitride/a-MoSx core-shell nanostructures which demonstrate negative photoresponsivity under 254 nm illumination and positive photoresponsivity under 365 nm illumination, which is rarely seen in traditional III-nitride nanowires.
“Photodetectors measure photon flux or optical power by converting the absorbed photon energy into electrical current, so-called photocurrent. In the operation of a photodetector, it is highly desirable that we can use the generated photocurrent, not only its magnitude but also its directionality to measure and diagnose the incident light signals. Consequently, once the photodetector demonstrates a dual-polarity photocurrent behavior upon different wavelength light illumination, we are able to distinguish different spectra bands.” Herein, Prof. Sun collaborated with other scientists and they propose to form III-nitride/MoS x core-shell nanowires for constructing spectrally sensitive photoelectrochemical photodetectors. Essentially, such a monolithically integrated core-shell nano-device architecture not only address issues of the nanowire surface states, but also expand the device functionalities by unleashing the full potential of both types of low-dimensional materials. As a result, the new a-MoS x /GaN core-shell nano-architecture propels superior device performance, exhibiting a benchmarking negative photoresponsivity of -100.42 mA·W −1 under 254 nm, and a positive photoresponsivity of 29.5 mA·W −1 under 365 nm illumination, which represents one of the best devices among the reported spectrally distinctive photosensors .”
“This vertical nanowire p-n heterojunction configuration based photoelectrochemical device presents a new universal photodetector architecture with ultrabroad wavelength coverage and selectivity that can span ultraviolet, visible, and/or infrared spectral range by constructing nanowire p-n heterojunctions composed of any binary or ternary III-V semiconductors (III- nitrides, arsenides, and phosphides etc.). This is ascribed to the unique one-dimensional structure of nanowires, which allows sufficient strain relaxation for epitaxial growth of a broad range of lattice-mismatched materials.” they added.
“The presented technique can be used in multiple-band and spectrally distinctive photodetection in building modern light-induced sensing systems, including colorful and filter-less imaging, portable spectrometer, artificial vision, bio-sensors and optically-controlled logic circuits. Particularly, for those emerging photoelectrochemical-type (PEC-type) photodetectors, they can be directly implemented in aqueous condition, such as in bio blood environment, seawater or underwater environment for light communication, photo-sensing and bio-detection, as compared with those conventional solid-state photodetectors that requires sophisticated packaging for aqueous application.” the scientists explain.
Light Science & Applications