High performance ultraviolet (UV) photodetectors based on semiconducting nanowires are expected to have extensive applications in UV-ray detection, optical communication and environmental monitoring. In this work, GaN nanowire photodetectors have been fabricated and giant UV photoresponse has been achieved with Pt nanoparticle (NP) modification. The peak responsivity and external quantum efficiency (EQE) of the GaN nanowire UV photodetector were increased from 773 to 6.39 × 104 A W−1 and from 2.71 × 105% to 2.24 × 107%, respectively, and the response time and sensitivity were improved greatly after Pt NP decoration on the GaN nanowire surface. Moreover, the Pt–GaN nanowire photodetector still presents its spectrum selectivity in the UV region. Our results reveal that Pt nanoparticles play a key role in enhancing the photodetection performance of the nanodevice due to the strong absorption and scattering of incident light induced by localized surface plasmon resonance (LSPR) and the improvement of interfacial charge separation owing to the special device configuration. These findings offer an efficient avenue toward the performance enhancement of GaN nanowire and related optoelectronic devices or systems.

Giant UV photoresponse of a GaN nanowire photodetector through effective Pt nanoparticle coupling

The detection of UV-A rays (wavelength of 320–400 nm) using functional semiconductor nanostructures is of great importance in either fundamental research or technological applications. In this work, we report the catalytic synthesis of peculiar bicrystalline GaN nanowires and their utilization for building high-performance optoelectronic nanodevices. The as-prepared UV-A photodetector based on individual bicrystalline GaN nanowire demonstrates a fast photoresponse time (144 ms), a high wavelength selectivity (UV-A light response only), an ultrahigh photoresponsivity of 1.74 × 107 A/W and EQE of 6.08 × 109%, a sensitivity of 2 × 104%, and a very large on/off ratio of more than two orders, as well as robust photocurrent stability (photocurrent fluctuation of less than 7% among 4000 s), showing predominant advantages in comparison with other peer semiconductor photodetectors. The outstanding optoelectronic performance of the bicrystalline GaN nanowire UV-A photodetector is further analyzed based on a detaile...

Ultrasensitive and Highly Selective Photodetections of UV-A Rays Based on Individual Bicrystalline GaN Nanowire

Core–shell Co3O4/ZnCo2O4 coconut-like hollow spheres are synthesized by a facile two-step method. As the anode of lithium-ion batteries, their reversible capacity is up to 1278 mA h g−1 at 0.1C rate and remains at 1093 mA h g−1 after 50 cycles, much higher than that of pure Co3O4. Even after 300 cycles (cycling for more than 4 months), their reversible capacity can maintain at 934 mA h g−1 at 0.2C rate. Such superior electrochemical performance (high reversible capacity, excellent long-term cycling stability and good rate capability) can be ascribed to the unique core–shell hollow structure, complex synergistic effect, good electrical conductivity and interfacial charging mechanism. The present results demonstrate that the core–shell Co3O4/ZnCo2O4 hollow spheres are promising anode materials for high-performance lithium-ion batteries.

Core–shell Co3O4/ZnCo2O4 coconut-like hollow spheres with extremely high performance as anode materials for lithium-ion batteries

Crystalline GaN nanosheets hold great challenge in growth and promising application in optoelectronic nanodevices. In this work, we reported an accessible template approach toward the rational synthesis of GaN nanosheets through the nitridation of metastable γ-Ga2O3 nanosheets synthesized from a hydrothermal reaction. The cubic γ-Ga2O3 nanosheets with smooth surface and decent crystallinity can be directly converted into hexagonal GaN nanosheets with similar morphology framework and comparable crystal quality in NH3 at 850 °C. UV–vis spectrum measurement reveals that the GaN nanosheets show a band gap of 3.30 eV with strong visible absorption in the range of 370–500 nm. The template synthetic strategy proposed in this work will open up more opportunities for the achievement of a variety of sheetlike nanostructures that can not be obtained through conventional routines and will undoubtedly further promote the fundamental research of newly emerging sheetlike nanostructures and nanotechnology.

Template Approach to Crystalline GaN Nanosheets.

Group-III-nitride semiconductors, including AlN, GaN, InN and their ternary, quaternary compounds, are promising electronic and optoelectronic materials for the applications in light emitting diodes, lasers, field emitters, photodetectors, artificial photosynthesis, and solar cells. Owing to their direct bandgaps ranging from near infra-red to deep ultraviolet. In recent years, the growth of group-III nitride nanostructures has been extensively explored. Herein, we provide a comprehensive review on the rational synthesis, fundamental properties and promising applications of group-III nitride nanostructures. Group-III nitride nanostructures with diverse morphologies, their corresponding synthesis methods and formation mechanisms involved are systematically compared and discussed, as well as the detailed factors that influence the optical and electrical properties of the nanostructures. The recent achievements gained in the fields of III-nitride nanostructures are highlighted, including light emitting diodes, laser diodes, photodetectors, solar cells, artificial photocatalysis, nanosensors, and nanogenerators. Finally, some perspectives and outlook on the future developments of III-nitride nanostructures are commented.

Recent progress in group III-nitride nanostructures: From materials to applications

Here, we report the origin of the yellow-band emission in epitaxial GaN nanowire arrays grown under carbon-free conditions. GaN nanowires directly grown on [0001]-oriented sapphire substrate exhibit an obvious and broad yellow-band in the visible range 400–800 nm, whereas the insertion of Al/Au layers in GaN–sapphire interface significantly depresses the visible emission, and only a sharp peak in the UV range (369 nm) can be observed. The persuasive differences in cathodoluminescence provide direct evidence for demonstrating that the origin of the yellow-band emission in GaN nanowire arrays arises from dislocation threading. The idea using buffering/barrier layers to isolate the dislocation threading in epitaxially grown GaN nanowires can be extended to the rational synthesis and structural defect controlling of a wide range of semiconductor films and nanostructures with superior crystal quality and excellent luminescence property.

Song Zhang

Papers

Origin of Yellow-Band Emission in Epitaxially Grown GaN Nanowire Arrays