In this study, we investigate the charge trapping in hydrogen-terminated diamond (HD) MOSFETs based on the transient drain current. The hole detrapping is reflected by monitoring the transient current after applying the filling voltages, and three distinct trap peaks are clearly identified using the Bayesian deconvolution. The energy levels are determined from temperature-dependent measurements to be approximately 0.47, 0.35, and 0.15 eV. Besides, the contribution of each trap to the transient current variation can be quantified using the differential amplitude spectra. Three kinds of bias conditions are designed to analyze the dependence of trap amplitudes on filling voltages, which reveals the strong correlation with threshold voltage shift and drain current reduction. By correlating these trap properties with electrical measurements, the physical locations of traps are identified at the interface, in the gate oxide, and in the diamond layer. Notably, the trap within the diamond is found to dominate the current collapse. This work provides profound insights into the trapping mechanisms limiting HD MOSFET performance, establishing a foundation for developing more reliable high-power diamond devices.

This work demonstrates the heteroepitaxial growth of single-phase β -(Al x Ga 1− x ) 2 O 3 on (010) β -Ga₂O₃ substrates via metalorganic chemical vapor deposition, achieving an aluminum composition of up to 22.6% with no phase segregation characterized by x-ray diffractometer. The surface morphology of epitaxial layer becomes rougher initially and then smoother with the increase of Al composition, suggesting that the rising Al composition leads to changes in the epitaxial growth mode. The fabricated MOSFETs based on β -(Al 0.09 Ga 0.91 ) 2 O 3 epitaxial film achieve an ultra-high breakdown voltage over 3000 V and a high average breakdown field of 2.3 MV cm −1 . This work underscores the potential of β -(Al x Ga 1− x ) 2 O 3 heteroepitaxy technique and showcases its suitability for high-voltage power device applications.

This paper demonstrates an integrated comparator based on a novel platform of GaN-based high electron mobility transistors (HEMTs) with low pressure chemical vapor deposition (LPCVD) SiNx as both gate dielectric and passivation layer. Solving the compatibility issue in device fabrication, both high-performance D-mode and E-mode GaN HEMTs have been realized and then loaded for circuits simulation. With careful determination of each device's performance, the designed comparator has been constructed, and its comparison range goes from 1 to 3.5 V at VDD = 5 V. Moreover, the comparator achieved a rise time of 754 ns at a driving frequency of 100 kHz, and maintained stable operation even at a high temperature of 200 degrees C. The comparator based on the new platform of p-GaN gated HEMTs with LPCVD SiNx passivation provides a new solution for GaN-based power ICs and holds great potential in wide applications.

This paper presents a broadband K/Ka-band parallel Doherty power amplifier (PA) implemented in 65-nm CMOS. To address the large footprint and limited bandwidth issues of conventional Doherty architectures at millimeter-wave (mm-wave) frequencies, this design proposes a compact transformer-based output combining network. By utilizing lumped-parameter equivalent models, the traditional three-transmission-line (three-Tline) structure—comprising the impedance inverter and the impedance scaling network—is merged and simplified into a combination of two transformer coils and a series capacitor. This structure not only minimizes the chip area but also effectively extends the operating bandwidth. Measurement results demonstrate that the PA achieves a flat gain response across the 22–30 GHz band. At 24 GHz, the saturated output power (Psat) is 18.45 dBm, and the peak power-added efficiency (PAEmax) reaches 32.1%. At 5.7-dB power back-off (PBO), the PAE remains at 20%, validating its potential for next-generation high-efficiency phased-array transmitters. Additionally, simulation results indicate that tuning the adaptive bias network (ABN) effectively enhances the large-signal performance of the PA under load mismatch conditions.

In this work, the high-power millimeter-wave limiter based on a gallium nitride (GaN) quasi-vertical structure Schottky barrier diode (SBD) is proposed and validated in the range of 30-36 GHz. The high-doping concentration and thin thickness of the n-layer GaN can effectively reduce the on-resistance of GaN SBD, thereby reducing the insertion loss of limiters. The limiter utilizes GaN MMIC technology to enhance the consistency of multistage circuit manufacturing. In addition, the limiter adopts a three-stage structure design and combines with the power division structure to optimize the power handling capability of the first-stage limiter, further improving the overall system output power capacity. The insertion loss of the limiter is less than 2 dB within the frequency range of 30-36 GHz. This limiter can withstand a pulse input power of 20 W without burning out. The limiter based on GaN SBD exhibits advantages in high frequency and high power.

A 28 GHz low-noise amplifier (LNA) fabricated in a 65-nm CMOS technology is presented. The LNA is designed with two common-source (CS) stages. An area-efficient triple-coupled transformer is adopted in this work. The weak coupling between the coils of the transformer generates a compensation current to neutralize the Miller capacitance of the LNA. The noise performence and stability is significantly boosted. The LNA achieves a peak gain of 13.58 dB with a 3-dB bandwidth of 8.2 GHz, covering 21.6 to 29.8 GHz. A noise figure (NF) of 2.97 dB is achieved at 26.5 GHz. At 28 GHz, the LNA exhibits an input 1-dB gain compression point (IP1dB) of -11.3 dBm. The power consumption is 12 mW from a 1-V supply.

Precise control of monolayer WSe2 growth is critical for electronic and optoelectronic applications. Here, we systematically investigate the effect of growth pressure on chemical vapor deposition-synthesized WSe2 on SiO2/Si substrates. By tuning the pressure from atmospheric pressure to 2 & times; 10(3) Pa, the domain morphology evolves from multilayer triangular flakes with thick centers and edges to uniform monolayers at 5 & times; 10(3) Pa and finally to hollow structures at ultra-low pressure due to H-2-assisted etching. Raman, photoluminescence, x-ray photoelectron spectroscopy, and x-ray diffraction analyses confirm high crystallinity, uniform thickness, and phase-pure 2H-WSe2 at optimal pressure. A microscopic growth mechanism is proposed: pressure controls the precursor mean free path, which governs collision frequency and flux, while higher edge surface energy and anisotropic armchair/zigzag attachment barriers direct preferential deposition. These findings establish pressure as a key parameter for reproducible, high-quality WSe2 monolayer growth

In this work, we demonstrate a significant improvement in the performance of GaN terahertz (THz) Schottky barrier diodes (SBDs) via the post-anode annealing (PAA) process. The breakdown voltage of GaN THz SBDs was increased from 15.14 V to 23.70 V, which effectively enhances the power density of the device. The annealing mechanism of the Ni/Au interface reveals that the PAA process significantly mitigates Schottky barrier inhomogeneity and reduces interface state density (NSS). High-resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM) images reveal evidence of alloying occurring at the Ni/GaN interface. Meanwhile, the alignment of triangular metal clusters along the step-flow direction indicates that the PAA process effectively suppresses metal-induced gap states resulting from step-flow morphology at the Ni/GaN interface, thereby promoting the formation of a high-quality Ni/Au contact. This mechanism significantly contributes to the enhanced performance of GaN THz SBDs. Hence, this approach provides an efficient solution for high-power THz source applications.

Interfacial and internal traps are the main factors limiting the performance and reliability of Ga2O3 Schottky barrier diodes (SBDs). Herein, the trap characteristics of Ga2O3 SBDs are investigated using the current transient method, elucidating the carrier trapping and detrapping processes. Under the forward and negative voltage stress, different traps can capture electrons from various sources. The test results show that there are five different types of electronic traps in the Ga2O3 device, and each trap corresponds to a different time constant, activation energy, and location. The activation energies of these traps are 0.089, 0.2, 0.81, and 0.95 eV, respectively. In addition, there exists a temperature-independent electronic trap whose behavior may be related to the direct tunneling process. Therefore, this method can be applied to the reliability study of Ga2O3 to achieve nondestructive characterization of Ga2O3 SBD traps.

This paper presents an ultra-high-power-density gallium arsenide (GaAs) power amplifier (PA) for K/Ka-band phased-arrays. To maximize the output power density under stringent layout constraints, a novel area-efficient coupled-line transformer structure is utilized in this work. The fragile air-bridge crossovers inherent in traditional GaAs transformers can also be eliminated with better mechanical reliability. Fabricated in a commercial 0.1-μm GaAs process, the proposed PA is designed based on a two-stage differential architecture and is biased in Class-AB operation. On-chip measurement results demonstrate that the PA achieves a small-signal gain of 20.4 dB over the operating bandwidth from 23 to 28 GHz. The measured saturated output power (Psat) reaches 28.1 dBm at 25 GHz, alongside a peak power-added efficiency (PAE) of 38.5%. With a core area of 0.71 mm2, the proposed PA realizes a power density of 909.4 mW/mm2, achieving the best power density among the reported GaAs-based PAs.

In this work, X-band aluminum gallium nitride (AlGaN)/gallium nitride (GaN) high-electron mobility transistors (HEMTs) on polycrystalline diamond (PCD) substrate with record RF performance and low channel temperature were fabricated and analyzed. Devices were prepared by using a room-temperature wafer bonding process. A thin bonding interface with a thickness of similar to 17 nm was realized to minimize the thermal boundary resistance (TBR). On-wafer load-pull measurements of the fabricated 4 x 100 mu m GaN HEMTs on diamond yielded a state-of-the-art RF output power density of 25.28 W/mm at 10 GHz with associated power-added efficiency of 33.43%. In addition, the temperature of GaN HEMTs on diamond was dramatically reduced by similar to 150 degrees C compared to the HEMTs on silicon carbide (SiC) substrate at a direct current (DC) power density of 31.5 W/mm. The results show that great performance improvements have been achieved for GaN HEMTs on diamond, which will enable the microwave devices to operate reliably at a high power density with a long lifetime.

Magnetometers based on nitrogen-vacancy (NV) centers in diamonds have been widely studied. With the use of purified diamond and magnetic flux concentrators (MFCs), the sensitivity of magnetic field measurement has been improved to the subpico-tesla level. However, diamond magnetometers face the challenge of achieving high sensing performance after integration. Here, we demonstrate an integrated fiber-coupled diamond magnetometer based on an MFC with both high sensitivity and a wide dynamic range. We sandwiched a nitrogen-doped diamond film of [111] crystal orientation between the two MFCs. With the polarization direction of the pump laser perpendicular to the NV center axis, the signal-to-noise ratio and its linearity with the magnetic field are enhanced. We demonstrate a sensitivity of 50 $${{\rm{pT}}}/\sqrt{{{\rm{Hz}}}}$$@0.01 Hz and 390(172) $${{\rm{fT}}}/\sqrt{{{\rm{Hz}}}}$$@ > 3 Hz while with a detection range of about 4 times the Earth’s magnetic field. This work demonstrates the feasibility of portable, highly sensitive diamond magnetometers that maintain a large dynamic range in various natural environments. Diamond magnetometers leveraging nitrogen-vacancy centers offer precise magnetic field measurements but struggle with integration and miniaturization. Here, the authors present an integrated fiber-coupled diamond magnetometer using magnetic flux concentrators, achieving 50 $${{\rm{pT}}}/\sqrt{{{\rm{Hz}}}}$$ sensitivity and a wide dynamic range, paving the way for portable, high-performance sensing in diverse environments.

This letter presents a 220-GHz subharmonic mixer based on a fully planar, waveguide-free circuit that uses only microstrip lines and a GaAs Schottky barrier diode (SBD) for enhanced integration capability. A key novelty is the adoption of a custom-designed coupled-line structure to replace traditional waveguide-based hybrids, which achieves effective signal combining and isolation between the local oscillator (LO) and radio frequency (RF) ports on-chip. Measured at room temperature, the mixer exhibits a single-sideband (SSB) conversion loss (CL) of less than 11 dB from 204 to 228 GHz, with a minimum of 8 dB at 220 GHz. The isolation between the RF signal and the second harmonic of the LO signal is greater than 25 dB. This work demonstrates a compact and low-cost solution for terahertz integrated systems.

This paper presents a compact passive mixed-type true-time delay (TTD) circuit for wideband phased-array systems. The proposed circuit cascades a reflective TTD and two APN-based TTDs. In the reflective TTD, an ultra-compact monolayer coupler is adopted to reduce gain and delay variation. Furthermore, slow-wave transmission lines (SW-TLs) are also utilized in this work to improve the overall area efficiency. The proposed circuit is implemented in a $65-\text{nm}$ CMOS process. It covers a frequency band of $\mathbf{2 1 - 3 1 ~ G H z}$. The measured delay coverage is 52.8 ps with a tuning step of 4.8 ps. The corresponding RMS delay error and gain error are less than 1.7 ps and 0.63 dB, respectively. Thanks to ultra-compact coupler and the SW-TLs, the chip core area is only $0.14-\text{mm}^{2}$. A delay-per-area of 377.14 $\text{ps} / \text{mm}^{2}$ is realized by this work.

This work demonstrates a significant advancement in high-power p-NiO/ beta -Ga2O3 heterojunction diode (HJD) technology. A large-area ( 2x 2 mm(2)) HJD is fabricated, achieving a remarkable combination of a 2870-V breakdown voltage (BV) and a 20-A forward current. This performance is enabled by a novel terminal structure incorporating a double-layered p-NiO film. The device exhibits a low specific on-resistance ( R-on,R-sp)of 14.4 m Omega center dot cm(2), yielding a high Baliga's power figure of merit (P-FOM) of 572 MW/cm(2) (calculated as P-FOM = BV2/ R-on,R- sp) . Furthermore, it displays excellent fast-switching characteristics, with an ultrashort reverse recovery time of 12.80 ns and a low reverse recovery charge of 19.70 nC. The surge current capability is confirmed to be 16 A at a voltage of 11.1 V. Temperature-dependent electrical characterization from 298 to 448 K reveals key insights. The forward current and turn-on voltage decrease linearly with increasing temperature, with a zero-temperature coefficient (ZTC) bias point observed at approximately 2.3 V. The reverse leakage current follows a thermally activated mechanism, as evidenced by a linear relationship between its natural logarithm and the reciprocal of absolute temperature behavior characteristic of a conventional p-n junction. These results underscore the broad prospects of Ga2O3 HJDs for next-generation high-voltage and high-power electronic applications.

This study investigates firstly the leakage-temperature correlation degradation mechanism of highly doped epitaxial β-Ga2O3 Schottky Barrier Diode (SBD) after 5 MeV proton irradiation. Experimental results show that post-irradiation, the carrier concentration decreases by 52.1% from 1.4×1016 cm-3 to 0.68×1016 cm-3, the Schottky barrier height rises from 0.81 eV to 0.93 eV, the ideality factor increases from 1.076 to 1.601, the specific on-resistance increases by over 17 mΩ • cm2, and the reverse leakage current increases by two orders of magnitude while reducing temperature sensitivity. On the other hand, pre-irradiation reverse leakage of the device—measured at 300-350K with reverse bias from -20 V to -200 V—is dominated by Poole-Frenkel Emission (PFE) with a deep trap state ΦT = 0.49 eV. For post-irradiation device, Trap-Assisted Tunneling (TAT) becomes dominant instead of PFE. TAT related to 0.22 eV and 0.43 eV two shallow trap states prevail two regions respectively at 300-350K from -130V to -200V, and at 300-330 K from -80V to -130V. PFE with the 0.52 eV trap state merely remains in a narrowed region spanning temperatures from 330K to 350K from -60 V to -130 V. This transition of mechanism is attributed to the synergistic effect of irradiation-induced shallow trap states with ΦT values of 0.22 eV and 0.43 eV coupling with anode-edge surface electric field concentration, which differs from the PFE-dominated failure in our low-doped β-Ga2O3 SBD. Thus, irradiation-introduced shallow trap states are the primary cause of reverse characteristic degradation and reduced temperature sensitivity in highly doped epitaxial β-Ga2O3 SBDs.