This paper proposes a Harris Hawks Optimization (HHO)-based approach for rapid small-signal modeling of GaN high electron mobility transistors. It pioneers the application of HHO to efficiently construct 19-element equivalent circuit models over the 0.1-40 GHz broadband. To address challenges including strong parasitic/intrinsic parameter coupling in high-dimensional space, broadband accuracy imbalance of conventional fitness functions, and parameter magnitude disparities, key innovations are introduced: sequential optimization of grouped parameters for decoupling, physical constraints for integrated circuits, parameter normalization, and a frequency-weighted fitness function. Experimental results demonstrate that the proposed method achieves 34.4% CPU time reduction with 16.1% higher accuracy in parasitic parameter extraction compared with conventional optimization methods, while outperforming genetic algorithm and particle swarm optimization algorithm in intrinsic parameter optimization with faster convergence, lower error, and no requirement for manual parameter tuning. Close agreement between measured and modeled S-parameters across 0.1-40 GHz validates the methodology's effectiveness.

In this paper, an ultra-low power, high-efficiency microwave rectifier based on adaptive voltage model is proposed. Targeting micro-watt power scenarios, the proposed model incorporates diode leakage loss and employs a power-adaptive turn-on voltage to accurately characterize the loss distribution and calculate the power conversion efficiency of diode. The maximum discrepancy between the model calculation and harmonic balance simulation is less than 1%. Guided by the theoretical calculations, the junction capacitance is optimized, and a trade-off between the turn-on voltage and leakage current is established to design a gallium nitride (GaN) Schottky barrier diode (SBD) tailored for ultra-low power rectification. A 2.4-GHz rectifier utilizing this GaN SBD is implemented, achieving a measured efficiency of 19.8% at an input power of -25 dBm. The performance of the high-efficiency rectifier validates the significance of the adaptive voltage model in guiding the design of ultra-low power harvesting systems.

In this paper, a device-circuit co-design approach for a 5.8-GHz rectifier is presented, utilizing doping-optimized quasi-vertical gallium nitride (GaN) Schottky barrier diodes (SBDs). To overcome the inherent performance limitations of fixed-parameter commercial diodes, a reverse-design methodology is proposed. By mapping epitaxial doping concentrations to device electrical parameters and decomposing the nonlinear rectification losses, the impact of drift-layer doping on the conversion efficiency is systematically analyzed. The analysis reveals that an optimal doping concentration of 2×1017 cm-3 minimizes the dominant losses. Accordingly, a custom quasivertical GaN SBD is fabricated, exhibiting favorable electrical characteristics, including a low turn-on voltage of 0.30 V, a breakdown voltage of 30 V, and a high cutoff frequency of 142 GHz. Experimental results demonstrate that the fabricated 5.8-GHz rectifier achieves a peak conversion efficiency of 70.8% at 15 dBm and a wide dynamic range of 19 dB (6-25 dBm). This performance successfully validates the proposed device-level optimization strategy for C-band wireless power transfer applications.

The non-Hermitian skin effect (NHSE), characterized by the accumulation of a macroscopic number of bulk states at system boundaries, is a hallmark of non-Hermitian physics. However, in higher dimensions, achieving deterministic control over where skin modes accumulate remains a major challenge. Here, we propose a versatile route to program the skin-mode localization site in two-dimensional non-Hermitian lattices by combining disorder with a static electric field. While the electric field alone suppresses the NHSE in a clean system, the introduction of disorder induces transverse wave-packet transport perpendicular to the field. In nonreciprocal lattices, when the nonreciprocal hopping is misaligned with the electric field, the hopping component perpendicular to the field guides wave-packet propagation and produces boundary localization. By tuning the relative orientation between the electric field and the nonreciprocal hopping direction, the boundary localization position can be continuously and arbitrarily controlled. We further demonstrate distinct geometry-dependent manipulation of skin modes in reciprocal lattices, where controllable boundary localization emerges solely from the lattice geometry. Our results establish a robust and broadly applicable route to engineer boundary accumulation and directed transport along prescribed directions in two-dimensional non-Hermitian systems, enabling reconfigurable wave routing in classical platforms and programmable transport functionalities in quantum settings.

Due to rapid carrier recombination and photodegradation, cadmium sulfide (CdS), an n-type semiconductor photosensitive material, has a low utilization efficiency that restricts its use in biosensing. A synergistic hole-trapping approach utilizing steric hindrance effects is proposed in this paper. First, chemical bath deposition (CBD) is used to create a Si/CdS n-n heterojunction on the n-type silicon (n-Si) substrate surface. Through interface engineering, this heterojunction reduces rapid carrier recombination by optimizing carrier transport paths. In order to capture photogenerated holes building up in the CdS valence band, ascorbic acid (AA), which is strongly electron-donating and oxidizable, is added concurrently. This dual approach improves sensor stability and successfully reduces CdS self-oxidation faults. The resultant photoelectrochemical (PEC) sensor detects amyloid-β42 (Aβ42), a crucial biomarker for early diagnosis of Alzheimer's disease (AD), with great precision. The following is how the central mechanism functions: Upon the specific binding of Aβ42 to the sensor surface aptamer, the induced steric hindrance prevents AA from diffusing to the electrode surface. This lessens AA's capacity to absorb photogenerated holes by reducing oxidation processes. As a result, the photocurrent drops, and the suppression magnitude (ΔI) shows a positive association with the concentration of Aβ42. The sensor has a linear range of 10-17‒10-12 g/mL under ideal conditions, and its limit of detection (LOD) is as low as 3.1 × 10-18 g/mL (S/N = 3). This cutting-edge detection technology has great application potential in the realm of accurate biomarker identification and provides a fresh approach for early clinical diagnosis of AD.

This article presents a microwave rectification lossy model for low- and ultralow-power rectifiers, enabling accurate quantification and analysis of rectification losses. The first step involves employing a physics-based diode loss model to calculate diode losses, specifically accounting for leakage loss. Subsequently, the impedance of diode encompassing higher order harmonic effects is obtained via fast Fourier transform (FFT). Building upon this, a microwave rectification lossy model is proposed using the concept of splitting algorithm to determine the optimal lossy matching network and appropriate diode parameters for microwatt-level rectification. A key finding indicates that the reduction of intrinsic diode loss achieved by a smaller junction capacitance is offset by an increase in matching network loss, resulting in a degradation of the overall rectifier efficiency. Based on this comprehensive analysis, a gallium nitride (GaN) Schottky barrier diode (SBD) and a 2.4-GHz rectifier are designed and fabricated. Experimental results demonstrate a power conversion efficiency (PCE) of 43.2% at -15-dBm input power, outperforming state-of-the-art designs and validating the accuracy and practical utility of the proposed model.

Hydrogen-terminated diamond (H-diamond) field-effect transistors (FETs) hold great promise for high-frequency and high-power electronic devices owing to their excellent two-dimensional hole gas (2DHG) conduction properties. However, traditional gold ohmic contacts suffer from poor adhesion and insufficient stability, limiting device reliability and integration. This work applies a tungsten (W) ohmic contact preparation method based on high-temperature hydrogen plasma treatment. By depositing W electrodes on an oxygen-terminated diamond surface followed by high-temperature H-plasma treatment, ohmic contact with resistivity of 34.39 Omega mm between W and 2DHG and robust mechanical stability are achieved. Furthermore, a normally-off H-diamond FET is successfully realized with an ALD-Al2O3 dielectric layer, in combination with the nitrogen impurities of the substrate. The device exhibits a threshold voltage of -1.22 V, an on/off ratio of similar to 10(10), a subthreshold swing of 254 mV/dec, and a maximum drain current density of -9.4 mA/mm. This study provides a stable ohmic contact solution for H-diamond FETs with significant process practicality.

This study investigates a negative temperature coefficient (NTC) diamond thermistor fabricated using selective epitaxial diamond film technology in the temperature range of 80-723 K. The device exhibits excellent sensitivity over a wide temperature range from 150 K to 477 K. It shows a high B value of 4241 K in the range of 150-298 K and a lower B value of 718 K in the range of 298-477 K. The latter reduction indicates the onset of hopping conduction. Above 477 K, the resistance tends to saturate due to full impurity ionization. Transient response measurements show a fast rise time of 0.792 s with good repeatability. This work demonstrates that selective epitaxial technology offers a promising route for fabricating high-sensitivity diamond NTC thermistors suitable for wide-temperature-range applications.

The conventional fabrication of vertical gallium nitride (GaN) Schottky barrier diodes (SBDs) requires a cathode-first process due to the high-temperature annealing for ohmic contact. This work proposes an anode-first process enabled by low-temperature ohmic-contact annealing. A SiCl4 inductively coupled plasma (ICP) treatment is first performed on the backside N-polar GaN surface to introduce nitrogen vacancies. Subsequently, the TiN/Au anode is deposited, followed by the Ti/Al/Ni/Au cathode. A low-temperature annealing step at $500~^{\circ }$ C simultaneously accomplishes the formation of the backside ohmic contact and the stabilization of the Schottky contact topside. After optimization, the backside ohmic contact exhibits a sheet resistance of $51.74~\Omega $ /◻, and a contact resistance of $1.07~\Omega \cdot $ mm. The anode Schottky contact shows a barrier height of 0.77 eV and an ideality factor of 1.06, yielding a low specific on-resistance of 0.50 m $\Omega \cdot $ cm2. This simplified process significantly improves the forward characteristics while reducing reverse leakage, offering a new pathway for the fabrication of vertical GaN power devices.

This paper presents a 2.4 GHz high-efficiency textile rectenna for microwatt-level microwave wireless energy harvesting on lossy flexible substrates. To enhance microwave power collection under microwatt excitation, a gain-enhanced textile patch antenna with a stepped radiating edge and an offset feed line is designed, achieving a measured gain of 7.4 dBi at 2.4 GHz with an overall size of 0.65λ×0.65λ×0.016λ. A gallium nitride (GaN) Schottky barrier diode (SBD) rectifier with a lumped-element matching network is then designed for microwatt rectification, whose power conversion efficiency (PCE) is improved to 22.5% at-20 dBm and the peak efficiency is 32.1% at-13 dBm. Wireless measurements under different transmission distances and orientation angles further show that the proposed rectenna delivers an average rectified voltage of 0.11 V and a rectenna PCE of 23.97% at 2.4 m, corresponding to a dc output power of approximately 2.37 μW, demonstrating its effectiveness for wearable microwatt-level microwave wireless energy harvesting.

In this work, we demonstrate the fabrication of gold-decorated silicon column array (Au/SiCAs) photoanodes for photoelectrochemical (PEC) nitrite detection. The SiCAs were synthesized on n-type silicon substrates via photolithography and anisotropic etching, after which Au nanoparticles were deposited by magnetron sputtering. The Au/SiCAs photoanodes exhibited a pronounced PEC photocurrent response under the simulated solar irradiation. For nitrite determination, the sensor achieved two broad linear ranges (10-500 μM and 2000-10,000 μM) with corresponding sensitivities of 0.25 and 0.33 μA·μM-1·cm-2, along with a detection limit of 0.25 μM (S/N = 3). Moreover, the sensor exhibited excellent selectivity, remarkable stability, and facile fabrication. Successful detection in real sample confirms its potential for practical applications. This study proposes a novel approach for precise and reliable PEC-based nitrite analysis.

This work presents a microwave rectification enhanced pressure sensor. The sensor consists of a 2.4-GHz GaN Schottky barrier diode (SBD)-based rectifier operating with a normally-off GaN high electron mobility transistor (HEMT) pressure sensor, forming a pressure sensing system by directly utilizing the HEMT as the rectifier's load. The rectifier not only provides power to the sensor via RF-to-DC conversion but also improves the GaN HEMT's pressure sensitivity through a positive feedback mechanism. Results show that its output voltage exhibits a significant response to pressure. The sensor achieves a sensitivity of 9.82mV/kPa/V within the 0-170kPa pressure range, which is 2.5times that of traditional GaN HEMT pressure sensors.

This work systematically investigated the high-temperature performance of an all-diamond UV detector utilizing heavily boron-doped diamond (BDD) as transparent electrodes. The dark current increases moderately from 5.65 & times; 10(-11) A at RT to 2.26 & times; 10(-10) A at 450 degrees C, while the photocurrent under 222 nm increases obviously, leading to the responsivity increasing from 0.07 A/W to 0.37 A/W. The UV-to-visible rejection ratio rises from 2.86 & times; 10(4) to 1.16 & times; 10(6). Dynamic response measurements reveals that the rise time increases slightly from 0.02 s to 0.1 s, while the decay time remains stable at 0.03 s, suggesting that the response speed is virtually unaffected by high temperatures. Furthermore, the optoelectronic properties of the detector remain consistent during continuous high-temperature operation and long-term tracking test, demonstrating excellent thermal stability. This study proves that the all-diamond detector with BDD transparent electrodes exhibits outstanding advantages in high-temperature stability and response performance, providing a promising pathway for the development of high-performance UV detection technology in harsh environments.

This article presents an AlGaN/GaN HEMT sensor functionalized with S‑carboxymethyl-L‑cysteine for rapid and selective detection of cadmium ions. These molecules are self-assembled on the gate surface via Au–S bonding, enabling specific chelation with Cd²⁺ through carboxyl groups, inducing surface potential changes that modulate the 2DEG density via the charge control mechanism, thereby shifting the transfer curve rightward and reducing saturation. Experimental results show that the sensor achieves a detection limit as low as 0.001 μg/L and exhibits a good linear response over a wide concentration range of 0.001–10 μg/L. The sensor shows a current sensitivity of 45.8 μA/decade, a voltage sensitivity of 82.14 mV/decade, and a response time of ~5 s. It exhibits high selectivity and the TiN/Au gate provides excellent stability in acidic media. This platform offers a reliable solution for on‑site, ultrasensitive Cd²⁺ monitoring in environmental waters.

In this letter, a novel Gallium Nitride (GaN) Schottky barrier diode (SBD) featuring a 50-nm-thick quasi-depleted layer (QL) is proposed to mitigate the trade-off between turn-on voltage ( V-on) and reverse leakage ( I-r) . By effectively extending the zero-bias depletion region into the underlying drift layer to suppress hopping leakage, the fabricated QL-SBD simultaneously achieves an ultra-low V-on of 0.2 V at 1 mA ( I-on ) and maintains a low Ir over the intended operating voltage range. Furthermore, the minimized zero-bias junction capacitance of 40 fF yields a cutoff frequency ( fT ) of 317.8 GHz, which translates into a high f(T)& times; log(10 )( I-on / Ir )/ V-on figure-of-merit for low power microwave rectification of 3320 GHz/V. A 2.6 GHz microwave rectifier is demonstrated using the QL-SBD, achieving power conversion efficiencies of 29.04% at -20 dBm, 20.82% at -25 dBm, and 14.86% at -30 dBm, the highest reported to date for GaN SBD-based rectifiers. The results underscore the immense potential of QL-SBDs for self-powered IoT sensor nodes and next-generation ambient energy harvesting applications.

In this work, a high-performance temperature sensor based on GaN Schottky barrier diode (SBD) fabricated on n(-)-GaN/n(+)-GaN structure was demonstrated over an ultra-wide range from 6 K to 523 K. The device exhibited significant temperature dependence of the turn-on voltage, which decreases from 0.70 V at 6 K to 0.12 V at 523 K. With temperature increasing, the ideality factor showed a rapid decrease tendency, while the barrier height increased, which could be attributed to the Schottky barrier height inhomogeneity. The forward anode voltage was linearly proportional to the temperature at a fixed current over the measured wide temperature range. The sensitivity, derived from the slope of the V-T curve, reached a maximum of 1.66 mV/K in the low-temperature range of 100-298 K at 1 mu A. The results demonstrated the feasibility of GaN SBD for ultra-wide temperature sensing, filling the gap in detection at extremely low temperatures down to 6 K and expanding applications in cryogenic environments and extreme high-temperature scenarios.

This work demonstrates an all-diamond solar-blind ultraviolet photodetector employing a heavily boron-doped diamond (BDD) thin film as a transparent electrode. This monolithic structure overcomes the optical blocking inherent to traditional metal electrodes while maintaining excellent interfacial characteristics. Under 222 nm illumination and a 10 V bias, the device achieves a responsivity of 49.8 mA/W, approximately one order of magnitude higher than that of a Ti-electrode counterpart. The UV-to-visible rejection ratio reaches 4.54 × 104, accompanied by a high photocurrent-to-dark current ratio of 441.8. Dynamic response measurements reveal fast rise and decay times of 0.13 s and 0.03 s, respectively, significantly outperforming the metal-electrode device. These results highlight the significant advantages of the all-diamond BDD electrode in responsivity, speed, and spectral selectivity, providing a promising approach for high-performance solar-blind UV detection.

This study embeds Pt nanoparticles into single-crystal diamond to enhance ultraviolet (UV) absorption through localized surface plasmon resonance (LSPR), and then, a UV photodetector based on a Pt-embedded diamond film was investigated. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy-dispersive X-ray spectroscopy (EDS) confirmed the dense encapsulation of similar to 60-nm Pt nanoparticles within the diamond epilayer, preserving its surface flatness and crystalline quality. X-ray photoelectron spectroscopy (XPS) revealed that the embedded metallic Pt-0 induced an upward valence band bending. Combined with their partially exposed morphology, these Pt particles acted as a conductive transition layer, facilitating the Ti/diamond ohmic contact. Under 222-nm illumination and -20-V bias, the Pt-embedded detector achieved a responsivity of 8.38 A/W and a UV/visible rejection ratio (R-222/R-405) of 1.65 x 10(4). The device also exhibited comparable response speed to a pure diamond photodetector with rise and fall times of 0.486 and 2.645 s, respectively. Finite-difference time-domain (FDTD) simulations verified that the performance enhancement primarily originated from the LSPR effect induced by Pt nanoparticles. This work demonstrates that metal nanoparticle embedding in single-crystal diamond is an efficient approach for high-performance UV photodetectors.

This study systematically investigates the effect of anode-cathode spacing on the temperature sensing performance of diamond Schottky barrier diodes fabricated via selective epitaxial growth over an extended temperature range up to 723 K. Variations in spacing were found to have no significant impact on the crystal quality of the selectively epitaxial diamond layer. As the spacing increases from 30 to 60 μm, the voltage sensitivity is significantly enhanced from 1.98 to 3.87 mV/K, which is primarily attributed to the increase in temperature-dependent series resistance with larger electrode spacing. Notably, a distinct deceleration in the forward voltage shifting rate is observed at elevated temperatures (>523 K), revealing a transport mechanism transition from a low-temperature resistance-dominated regime to a high-temperature pure Schottky barrier-controlled regime. Additionally, all fabricated devices exhibited rapid dynamic response speeds compared to conventional Pt thermistor sensors. These findings provide a critical experimental foundation for optimizing the structural design of selective epitaxial diamond Schottky barrier diode-based temperature detectors.