AlGaN-based Far-UVC LEDs are highly promising for biosafe sterilization applications, yet their performance is severely limited by low internal quantum efficiency (IQE) and light extraction efficiency (LEE). Although LEE can be enhanced by extrinsic photonic engineering, it is fundamentally constrained by the intrinsic degree of polarization (DOP) of the quantum well (QW) structure, which determines the fundamental limit of vertical emission. Conventional QW design strategies typically treat IQE and DOP as independent parameters, ignoring their potential physical coupling. Herein, we identify a fundamental trade-off between IQE and DOP in compositionally graded QWs: designs favoring higher IQE often degrade polarization properties, and vice versa. To break this trade-off, we propose a novel ultra-thin QW architecture that simultaneously boosts both performance metrics. The pronounced quantum confinement in the ultra-thin QW significantly raises the confined sub-levels, overcoming the carrier localization in polarization-induced triangular potentials and greatly enhancing electron–hole wavefunction overlap to improve IQE. Meanwhile, such strong confinement effectively tailors the valence band ordering, yielding a higher DOP. This design strategy offers a viable route toward high-performance Far-UVC LEDs.

Interface engineering is an effective strategy for enhancing the performance of optoelectronic devices. In this work, we develop a reliable interface modulation approach specifically for III-nitride materials by fabricating low-dark-current GaS/GaN heterojunction ultraviolet (UV) photodetectors (PDs) with controlled polarity and dimensionality, thereby improving both responsivity and detectivity. Compared with Ga-polar devices, the Npolar heterojunction PDs exhibit markedly superior performance: the responsivity increases from 1.13 mA/W to 143 mA/W, the specific detectivity improves from 3.4 x 108 Jones to 6.58 x 1010 Jones, and the linear dynamic range is enhanced from 19 to 50 dB. Simulation results of the two heterojunction interfaces reveal that these performance enhancements arise from a stronger built-in electric field in the N-polar heterojunction, which facilitates more efficient separation of photogenerated electron-hole pairs. Furthermore, we investigate the potential of these devices for low-noise UV optical imaging, enabled by their low dark current and ultra-low NEP. Overall, this work demonstrates an effective strategy for tuning the performance of III-nitride heterojunctions and highlights their strong potential for low-noise UV detection applications.

Optoelectronic synapse devices hold enormous application prospects in neuromorphic machine vision but suffer from critical challenges including heteroepitaxial lattice mismatch and cumbersome fabrication processes. 4H-SiC offers distinct merits for high-performance neuromorphic devices due to its wide bandgap, high defect tolerance, and CMOS compatibility. Herein, we fabricated ultra-low-power photonic synapses based on MoS2/4H-SiC heterostructures, realizing faithful emulation of biological visual information processing. Under 405-nm illumination (5.05 mW · cm−2), the device exhibited amplified photoresponse with increasing light pulses: excitatory postsynaptic current change (ΔEPSC) rose progressively to saturation, mimicking biological reinforcement learning. It also achieved non-volatile long-term memory, with current remaining stable after light cessation. Pair-pulse facilitation (PPF) experiments showed a peak PPF index of 134.4

The development of high-quality, stable, and cost-effective micro/ nano dual-band lasing remains a crucial challenge for multifunctional applications. In this study, we demonstrated high-Q dual band whispering gallery mode lasing in an independent core-shell microdisk, emitting both ultraviolet and blue lasing. The GaNbased microdisk with InGaN/GaN quantum wells served as the core, while a SiO2 layer was deposited on the sidewalls to construct the core-shell microdisk. This independent structure was fabricated using the graphically epitaxial lift-off method, which effectively mitigates light leakage issues associated with the substrate and facilitates flexible device integration. Compared to the microdisk without a SiO2 shell coating, the threshold of ultraviolet lasing in the core-shell microdisk was reduced by 1.6 times, the quality factor (Q-factor) was enhanced by 21.7%, and blue lasing was successfully achieved. The underlying physical mechanisms were thoroughly analyzed through steady-state and time-resolved photoluminescence, along with finite-difference time-domain simulations. Furthermore, cooling from 300 K to 100 K could significantly enhance the lasing performance, increasing the Q-factor by factors of 1.7 and 1.9 in the ultraviolet and blue bands, respectively. Additionally, due to thermal expansion and thermo-optical effects, the blue lasing mode exhibits a temperature-dependent wavelength shift with a slope of-0.007 nm/K. The generation and optimization of dual-band lasing within a single microcavity offer new opportunities for broadband optical communication, high-sensitivity multi-wavelength biosensing, multi-label biomedical imaging, and high-density optical storage.

This paper presents the design of a level shifter for GaN power device half-bridge drivers. The proposed level shifter employs a current mirror for level shifting, significantly reducing the propagation delay. Building upon the conventional pulse-triggered level shifter architecture, this design leverages a current mirror to replicate parasitic currents, thereby weakening the effects of parasitic currents. Additionally, an output feedback mechanism is introduced to further suppress the node voltage fluctuations caused by parasitic currents generated by common-mode transient voltage. The level shifter is implemented using a $0.18\mu \mathrm{m}$ HVBCD process, and simulations are performed on the Cadence platform. Post-layout simulation shows that the design achieves dV/dt immunity up to 200V/ns with the propagation delay of 1.5 ns.

Free-electron laser (FEL) operating in the terahertz (THz) spectral regime has found significant applications in diverse research fields. Nevertheless, fiber-based THz modulators based on FEL systems remain relatively underexplored. This study proposes a THz modulator based on side-polished fiber integrated with GaAs/Au nanoparticles (Nps) that demonstrates effective compatibility with the China Academy of Engineering Physics' THz FEL system. The modulator operates under high-power THz pulses (3 W) and achieves effective amplitude modulation across a broad frequency range from 1.6 to 3.0 THz. Owing to structural mode resonance, the modulator reaches the maximum modulation depth at 2.7 THz. The modulation depth was further enhanced by simultaneously applying optical and electrical modulation, i.e., optoelectronic synergistic optimization. Under a pump laser power of 235 mW, the peak modulation depth increases from 58.56% (at 0 V) to 67.11% (under 2.0 V). This investigation provides a solid foundation for the future application of fiber-based THz modulators in materials science, atomic physics, and biomedical studies, demonstrating their potential to advance the development of THz technology.

Acoustic sensing plays a vital role in underwater detection, communication, and biomedical diagnostics. However, conventional acoustic sensors suffer from various limitations: capacitive and piezoelectric sensors exhibit narrow bandwidth and low sensitivity and rely on external power, while optical sensors, despite their high sensitivity, require complex instrumentation and high costs. Here, an ultra‐wideband acoustic sensor (UWAS) is presented that operates via hybrid triboelectric‐piezoelectric coupling and integrates a trapezoidal‐grooves acoustic metasurface lens (PTGs‐AML). The periodic trapezoidal grooves significantly enhance acoustic radiation, increasing it by up to 255% at 10 MHz compared to conventional rectangular grooves. This enhancement improves acoustic focusing and suppresses sidelobe effects. The UWAS delivers a broad frequency response (20 Hz–50 MHz), high sensitivity (11.3 V Pa −1 at 60 kHz), and a signal‐to‐noise ratio of 67 dB (at 150 kHz). Its response is frequency‐dependent: omnidirectional at 53 Hz, unidirectional at 50 kHz, and multidirectional at 13 MHz. The enhanced energy localization enabled by PTGs‐AML supports high‐fidelity audio recording, environmental noise monitoring, and biomedical imaging, including venous thrombosis detection and knee effusion diagnosis. This self‐powered and scalable sensor provides a low‐cost solution for diverse acoustic applications. Furthermore, the metasurface design offers a generalizable strategy to broaden the bandwidth of conventional capacitive and piezoelectric sensors, paving the way for next‐generation acoustic sensing technologies.

This study addresses the challenges of strong empirical dependence, high trial-and-error costs, and technical difficulties in mechanical property prediction for 12Cr2Mo1V large cylindrical forgings by proposing a machine learning-based performance prediction methodology. Industrial data from hot forging production lines were collected, preprocessed, and utilized to comparatively analyze the predictive performance of various computational models. Results demonstrate that Support Vector Machine (SVM) exhibits superior performance in predicting critical indicators including grain size, normal-temperature tensile strength, and high-temperature tensile strength. Experimental validation confirmed strong consistency between model predictions and empirical measurements, verifying the methodology's practical applicability. Integration with the Mean Impact Value (MIV) algorithm elucidated the causal relationships between process parameters and the mechanical properties of large cylindrical forgings. This research establishes a data-driven predictive framework for optimizing the forging process of 12Cr2Mo1V steel, effectively reducing trial-and-error expenses while enhancing quality consistency in large pressure vessel forgings, with significant implications for high-performance material design and manufacturing.

Although electrochemical epitaxial lift-off (EELO) has recently been developed to successfully obtain freestanding nitride membranes and fabricate various novel optoelectronic devices, controllability of the electrochemical reaction and subsequent device fabrication strategies are yet to be explored. In this study, the analysis using Tafel extrapolation reveals that the lift-off rate of EELO with nitric acid as the electrolyte is high and the freestanding 3 x 3 micro-LED array membranes obtained have low n-GaN surface roughness, which facilitates the subsequent deposition of electrode materials and bonding. The reaction dynamics suggests that NO2 is generated during the EELO process, and NO2 is readily soluble in the nitric acid electrolyte, thus promoting the complete corrosion of the sacrificial layer. The turn-on voltage of a single micro-LED device is 2.38 V, with an ideality factor of n = 1.16, indicating low contact resistance and good current spreading. At a reverse bias of -5 V, the leakage current of the device remains on the order of 10-11 A. This results from the optimization of the EELO process and the availability of devices with low surface roughness. This low-cost and efficient substrate stripping method can be employed to integrate various III-nitride device elements.

This paper presents the design of a high-precision bandgap reference source with piecewise compensation and no operational amplifier. The circuit uses a current-mode bandgap reference without an operational amplifier as the first-stage compensation circuit. By adjusting the resistance values in the first-stage compensation circuit, the output curve of the bandgap reference is shifted from the mid-temperature region to the high-temperature region. After the shift, the curve only shows a larger slope in the low-temperature region. Negative temperature coefficient current is injected into the low-temperature region to raise the voltage and complete the compensation. Simulations were conducted using a 0.18µm CMOS process on the Cadence Virtuoso platform. The simulation results show that the compensated reference voltage exhibits a temperature drift of only 0.741 ppm/°C in the temperature range of -40°C to 125°C.

To elucidate the impact of the solid solution process on the microstructure and mechanical properties of Cr−Mn−N austenitic stainless steel, comparative experiments were conducted with varying solid solution temperatures and durations. The results indicate that the grain size gradually increases with increasing solid solution temperature and duration. When the temperature reaches a high level (1120 °C) or is maintained at 1080 °C for an extended period (25 min), the smaller grains are progressively engulfed by the adjacent larger grains, resulting in a swift augmentation in grain size and heterogeneity. In the hot rolled specimens, a considerable quantity of precipitates with large sizes (200 nm) is observed. After the solid solution treatment, the precipitate dimensions are significantly diminished, and their volume fraction is significantly influenced by the temperature of the solid solution. EDS and HRTEM were used to determine that the main precipitated phases after hot rolling and solid solution treatment were Cr7C3, Cr23C6 and Cr2N. With the increase in the solid solution temperature and time, the increment of grain boundary strengthening and dislocation strengthening decreases, while the contribution of precipitation strengthening initially increases before subsequently decreasing, which is the reason why the experimental steels with solid solution temperature of 1040 °C and solid solution temperature of 1080 °C held at 5 min still have the same mechanical properties despite the difference in solid solution treatment processes.

The development of high-quality, stable, and cost-effective micro/nano dual-band lasing remains a crucial challenge for multifunctional applications. In this study, we demonstrate high-Q dual-band WGM lasing in an independent core-shell microdisk, emitting both ultraviolet and blue lasing. The GaN-based microdisk with InGaN/GaN quantum wells serves as the core, while a SiO2 layer is deposited on the sidewalls to construct the core-shell microdisk. This independent structure is fabricated using the graphically epitaxial lift-off method, which effectively mitigates light leakage issues associated with the substrate and facilitates flexible device integration. Compared to the microdisk without a SiO2 shell coating, the threshold of ultraviolet lasing in the core-shell microdisk is reduced by 1.6 times, the Q-factor is enhanced by 21.7%, and blue lasing is successfully achieved. The underlying physical mechanisms are thoroughly analyzed through steady-state and time-resolved photoluminescence, along with finite-difference time-domain simulations. Furthermore, cooling from 300 K to 100 K significantly enhances lasing performance, increasing the Q-factor by factors of 1.7 and 1.9 in the ultraviolet and blue bands, respectively. Additionally, due to thermal expansion and thermo-optical effects, the blue lasing mode exhibits a temperature-dependent wavelength shift with a slope of -0.007 nm/K. The generation and optimization of dual-band lasing within a single microcavity offer new opportunities for broadband optical communication, high-sensitivity multi-wavelength biosensing, multi-label biomedical imaging, and high-density optical storage.

Effect of chemical composition and isothermal treatment duration on nano-bainite steels is investigated in this work. The steels that contain Co, V and Al elements with high C are designed and produced. The nano-bainite microstructures can be obtained by the isothermal treatment in the Co and Al co-alloyed sample. Its mechanical properties and wear resistance performance are tested. Its microstructures were detected using a FESEM. After the steel is austensitized at 950 ℃ for 30 minutes and is subsequently isothermally-treated at 260 ℃ for 2 hours, the nano-bainite structures can be obtained, whose microstructures also contain martenite and residual austenite in addition to nano-bainite. The isothermal time of 120 minutes is enough to obtain sufficient nano-bainite, which forms due to the addition of both Al and Co, which accelerate the austenite → bainite transformation, since Al and Co increase the free-energy difference between ferrite and austensite and the reaction rate for obtaining nano-bainites. The fracture toughness of the nano-bainite steel obtained by the isothermal transition is obviously better than the quenching + tempering steel for the Co and Al co-alloyed sample. The fracture morphology of the Charpy impact test shows that the fracture is ductile. Although nano-bainite steel has the poor wear-resistance performance the initial stage compared to quenching + tempering steel, it shows more and more wear resistance performance with increasing wear time.

The performance of semiconductor photodetectors (PDs) is primarily determined by their optical absorption efficiency and carrier transport capability. In this study, high-performance ultraviolet (UV) PDs based on 1transferred GaN nanobelt (NB) arrays were fabricated and the mechanisms behind their superior performance was elucidated. The carriers' transport characteristics under dark conditions were identified as the thermionic emission (TE) mode, while the photogenerated carriers' transport mechanism involved coupling to the photoemission and field emission (FE) modes. The GaN NB PD exhibits high performance, which can be applied for detecting weak UV light even under high temperature. Compared to pre-transferred GaN NBs and transferred GaN film devices, the transferred GaN NB devices exhibited exceptional photoelectric properties attributed to their high resistance and excellent orientation movement of photo-generated carriers in NBs. Finite-difference time-domain (FDTD) simulations and photoluminescence studies of transferred GaN NBs highlighted their outstanding optical absorption and waveguide properties. The analysis of electron transport mechanisms in highperformance GaN PDs further highlights the potential of high-resistance GaN NB arrays for UV PD applications.

In recent years, 2D/3D heterojunction electronic devices have attracted considerable attention. As the size decreases, enhancing the speed of MOSFETs, reducing the subthreshold swing (SS), and lowering the power consumption (P) have become challenging. Therefore, in the post-Moore era, in response to the continuation of Moore's law, junction field-effect transistors (JFETs) based on mixed-dimensional MoS2/GaN heterojunctions are proposed via thickness engineering. Accordingly, flat hetero interface and large potential barrier height of 5 eV across the heterojunction, an ultra-low SS of 60.9 mV dec(-1) (The Boltzmann limit is 60 mV dec(-1)) is achieved at V-ds = 0.1 V when the MoS2 thickness is 10 nm. Additionally, a high I-on/I(off )ratio of 107 and a saturation current density (J(ds)) of 0.16 mu A mu m-1 is achieved. As the thickness of MoS2 increased from 6 to 16 nm, the working mode transitioned from enhancement mode to depletion mode. The depletion region across the channel is verified using computer-aided design technology. Finally, an N-type load inverter with a maximum voltage gain of 4 and a minimum static P of 25 nW is applied. Overall, the work provides a universal strategy for constructing a series of high-performance transition metal dichalcogenide/GaN JFETs.

Performances of plasmon mediated optoelectronic devices are mainly limited by the hot carrier injection efficiency in metal-semiconductor plasmonic heterojunctions. Herein, the piezo-phototronic effect was used to promote hot-electron injection in Au/GaN plasmonic heterojunction, and the dynamics of hot-electron transport were investigated. The lateral and vertical Au/GaN plasmonic heterojunction devices were fabricated based on freestanding GaN film. The comparisons of hot-electron transport behaviors and photoresponse performances between lateral and vertical Au/GaN plasmonic heterojunction devices for sub-bandgap photodetection were systematically investigated. The photoresponse current of vertical heterojunction device is three orders of magnitude higher than lateral heterojunction device owing to the shortened electron transport path. The height of Schottky barrier at the heterojunction interface was tuned by the piezo-phototronic effect to enhance the injection efficiency of hot-electron. Optimized by the piezo-phototronic effect, the photoresponse current increases by nearly 89% under an applied compressive strain of 0.57% and the hot-electron injection efficiency was increased from 37.50% to 90.45%. The manipulating dynamic transport process of hot-electron under the regulation of applied strain is further confirmed by using transient absorption (TA) spectral measurement. This work provides a new architecture for efficient sub-bandgap photodetection based on GaN, and provides insight into the hot-electron dynamics in metal–semiconductor heterostructures.

This work demonstrates a WSe2/GaN heterojunction with different bandgaps and dimensionality for a high performance visible/ultraviolet dual-band photodetector. Two-dimensional (2D) p-type WSe2 was stacked on top of three-dimensional (3D) n-type GaN, enabling good construction of p-n junction at the interface, and thus exhibiting an excellent current rectification behavior and junction field-effect property. As a junction field-effect transistor (JFET), the device with WSe2 as a channel and GaN as a gate exhibits good transfer and output characteristics. In such a configuration, the device can be operated in the visible band with a responsivity of 98.67 A W-1 under 635 nm light illumination. By configuring the source/drain terminals on GaN, the device where GaN acts as a channel and WSe2 is sensitized on top is switched into the ultraviolet band. Under 325 nm light illumination, the responsivity (R) and specific detectivity (D*) can reach up to 7863.5 A W-1 and 1.27 x 10(14) Jones, respectively, far exceeding the state-of-the-art 2D- and GaN-based ultraviolet photodetectors. This work develops a mixed-dimensional WSe2/GaN junction for high performance dual-band photodetectors.

The mechanical behavior and microstructural evolution of an Fe-30Mn-3Al-3Si twinning-induced plasticity(TWIP)steel processed using warm forging was investigated.It is found that steel processed via warm forging improves comprehensive mechanical properties compared to the TWIP steel processed via cold rolling,with a high tensile strength(Rm)of 793 MPa,a yield strength(RP)of 682 MPa,an extremely large RP/Rm ratio as high as 0.86 as well as an excellent elongation rate of 46.8%.The microstructure observation demonstrates that steel processed by warm forging consists of large and elongated grains together with fine,equiaxed grains.Complicated micro-defect configurations were also observed within the steel,including dense dislocation networks and a few coarse deformation twins.As the plastic deformation proceeds,the densities of dislocations and deformation twins significantly increase.Moreover,a great number of slip lines could be observed in the elongated grains.These findings reveal that a much more dramatic interaction between microstructural defect and dislocations glide takes place in the forging sample,wherein the fine and equiaxed grains propagated dislocations more rapidly,together with initial defect configurations,are responsible for enhanced strength properties.Meanwhile,larger,elongated grains with more prevalently activated deformation twins result in high plasticity.

AlGaN DUV light emitting diodes (DUV-LEDs) (275 nm emission) are safe, eco-friendly and smart alternatives for inactivating viruses and bacteria. However, DUV-LEDs suffer from the main bottleneck of low external quantum efficiencies, which are strongly associated with the low light extraction efficiency caused by the strong optical polarisation of Al-rich AlGaN. Optical simulation results show that the luminous intensity of DUV-LEDs was increased by 10% owing to the synergistic effect of the sidewalls and substrates. The optical power of DUV-LEDs was increased to 16.8%, the far-field pattern was expanded to 130 degrees and the emission intensity was more focused on the central region, proving that the highly reflective sidewalls and substrates could re-direct the sideways-travelling photons for extraction. Moreover, we also investigated the reflective mechanism of Al/MgF2 layers. Optimizing the refractive index distribution of Al/MgF2 layers could change the electric field intensity and improve the reflectivity. At the same time, the temperature of the sample after coating was significantly reduced by 6.83%. Thermal radiation benefits and the high stability of bonding interfaces are the main reasons to reduce the temperature of DUV-LEDs after Al/MgF2 coating. The present strategy is proposed from the point of view of chip fabrication, which is cost-effective and able to be manufactured at a large scale.