Observation of polarity-switchable photoconductivity in III-nitride/MoSx core-shell nanowires

Abstract

III–V semiconductor nanowires are indispensable building blocks for nanoscale electronic and optoelectronic devices. However, solely relying on their intrinsic physical and material properties sometimes limits device functionalities to meet the increasing demands in versatile and complex electronic world. By leveraging the distinctive nature of the one-dimensional geometry and large surface-to-volume ratio of the nanowires, new properties can be attained through monolithic integration of conventional nanowires with other easy-synthesized functional materials. Herein, we combine high-crystal-quality III-nitride nanowires with amorphous molybdenum sulfides (a-MoSx) to construct III-nitride/a-MoSx core-shell nanostructures. Upon light illumination, such nanostructures exhibit striking spectrally distinctive photodetection characteristic in photoelectrochemical environment, demonstrating a negative photoresponsivity of −100.42 mA W−1 under 254 nm illumination, and a positive photoresponsivity of 29.5 mA W−1 under 365 nm illumination. Density functional theory calculations reveal that the successful surface modification of the nanowires via a-MoSx decoration accelerates the reaction process at the electrolyte/nanowire interface, leading to the generation of opposite photocurrent signals under different photon illumination. Most importantly, such polarity-switchable photoconductivity can be further tuned for multiple wavelength bands photodetection by simply adjusting the surrounding environment and/or tailoring the nanowire composition, showing great promise to build light-wavelength controllable sensing devices in the future.

Ultraviolet Exciton-Polariton Light-Emitting Diode in a ZnO Microwire Homojunction

“…Ultraviolet (UV) light sources, including light-emitting diodes (LEDs) and laser diodes (LDs), are of fundamental interest in a wide range of applications, e.g., bioanalytical, material processing, water purification, plant lighting, free-space optical communication, disinfection, and medical diagnostics. − Traditionally, UV light sources are mainly based on semiconductors with bandgap energies larger than 3.0 eV, such as SnO 2 , ZnO, GaN, etc. − Among these, GaN-based materials are the most commercially used in the design and fabrication of UV LEDs and LDs due to the successful manufacture of light emitters with reasonable p-type conductive characteristics. ,,− However, when working at high current injection levels, these optoelectronic devices would suffer a severe reduction of the internal quantum efficiency (IQE), the so-called efficiency droop. , That is caused by high in-plane strain, strong piezoelectric polarization fields, inevitable carrier leakage, and so forth. ,, Moreover, the realistic applications of GaN-based micro/nanoscale LEDs and LDs are hindered by the synthesis of high-quality nano/micromaterials, which are commonly based on time-consuming and expensive single-crystal synthesis techniques; high vacuum and high temperature are necessary for these synthesis techniques. − Briefly speaking, the achievement of low-cost and high-quality single-crystalline nano/micromaterials, especially for commercial manufacture of low-dimensional UV LEDs and LDs, still remains a long-term and arduous task.…”

“…14,15 That is caused by high in-plane strain, strong piezoelectric polarization fields, inevitable carrier leakage, and so forth. 14,16,17 Moreover, the realistic applications of GaN-based micro/nanoscale LEDs and LDs are hindered by the synthesis of high-quality nano/micromaterials, which are commonly based on time-consuming and expensive singlecrystal synthesis techniques; high vacuum and high temper-ature are necessary for these synthesis techniques. 18−20 Briefly speaking, the achievement of low-cost and high-quality singlecrystalline nano/micromaterials, especially for commercial manufacture of low-dimensional UV LEDs and LDs, still remains a long-term and arduous task.…”

Structural designs of AlGaN/GaN nanowire-based photoelectrochemical photodetectors: carrier transport regulation in GaN segment as current flow hub

“…[25][26][27] In recent years, the spectral distinguishable PEC PDs have been studied by some groups. [30][31][32][33][34] For instance, Tang's group demonstrated the opposite photocurrents using α-Ga 2 O 3 nanorods∕Cu 2 O p-n junction at 254 and 365 nm illuminations; however, the photocurrent (0.42 μA cm −2 with 254 nm and −0.57 μA cm −2 with 365 nm light) was small in the bipolar photoresponse devices. 30 Alternatively, Hoang et al 31 proposed the dual-plasmon device based on the Au nanoparticles∕TiO 2 ∕Au film, realizing the opposite photocurrents by tuning the hot-electron interplay from localized and propagating plasmons.…”

Photocurrent Polarity Switching and Enhanced Photoresponse in Silver Nanoparticles Decorated a-GaN-Based Photodetector

“…However, after the decoration of the Ag NPs on the a -GaN-based PD, positive photoconductivity (PPC) has been observed, with a reduced value of the dark current. Recently, a lot of research has been focused on devices exhibiting the unique phenomenon of polarity flipping due to their numerous advantages. ,, This peculiarity has been attributed to the passivation of defect states by the application of Ag NPs, which is corroborated by the photoluminescence spectra of the a -GaN and Ag NPs-modified a -GaN. The Ag NPs-modified PD exhibits multifold enhancement in the performance metrics of the detector, and the mechanism of photodetection has been elucidated with the help of energy band diagrams.…”

“…Recently, a lot of research has been focused on devices exhibiting the unique phenomenon of polarity flipping due to their numerous advantages. 6,16,17 , rplane sapphire) was cleaned through the standard cleaning process reported elsewhere, 7 before being loaded into the growth chamber. A base vacuum of ∼9 × 10 −10 mbar was achieved, followed by thermal cleaning of the substrate at 860 °C for 30 min.…”