In this work, a novel Schottky-gated p-channel GaN field-effect transistor (PFET) with a tunable n-GaN sub-gate layer is investigated. Terminal-current analysis under the actual drain-bias condition shows that the gate-current contribution remains limited within the defined effective operating range of VGS ≥ −3.2 V, whereas gate-related current becomes significant at more negative gate biases. Carrier-resolved and spatial current analyses further confirm that, within this operating range, the drain current is predominantly carried by holes through an interfacial hole channel near the p-GaN/AlGaN heterointerface. Benefiting from the intentionally introduced p–n junction beneath the groove gate, the built-in electric field effectively depletes the p-GaN channel, enabling a robust transition from depletion-mode to enhancement-mode (E-mode) operation. By precisely scaling the n-GaN layer thickness (0–5 nm) and donor concentration (3.0 × 1017 cm−3 to 3.0 × 1019 cm−3), the buried p-n junction modulates the depletion condition and hole distribution beneath the gate. The optimized device exhibits a significantly improved subthreshold swing (SS) of 348 mV/dec, while maintaining a stable ION/IOFF ratio on the order of 102. This tunable sub-gate architecture provides a highly flexible platform for optimizing E-mode GaN PFETs, showing great promise for high-performance complementary logic applications.

In this study, a memristor with an Al/aluminum nitride (AlN)/Pt structure was fabricated, and the coexistence of bipolar resistance switches (BRS) and unipolar resistance switches (URS) was observed. The device exhibits a high resistance state (HRS) with a resistance value exceeding 10(5)Omega for both switching modes. Remarkably, the device demonstrates excellent retention characteristics, maintaining stability for up to 10(4) s. Endurance testing revealed that the device can sustain over 10(3) DC switchingcycles, with resistance switching ratios greater than 10(2) in BRS mode and exceeding 10(3) in URS mode. To investigate the underlying conduction mechanisms, we performed conductive atomic force microscopy (C-AFM) measurements coupled with current-voltage (I-V) curve fitting analysis. Our findings reveal that the low-resistance state (LRS) conduction is governed by the formation of conductive filaments (CFs), while the forming process exhibits carrier transport characteristics consistent with Schottky emission. Both BRS and URS modes in the HRS regime demonstrate space-charge-limited current (SCLC) conduction behavior. Furthermore, temperature-dependent resistance measurements of the LRS suggest that the CFs are predominantly composed of Al atoms, providing crucial insights into the atomic-scale switching mechanisms in this memristive system.

Boron-doped diamond (BDD) epitaxial layers were successfully synthesized on intrinsic single-crystal diamond substrates using a microwave plasma chemical vapor deposition (MPCVD) system. Secondary ion mass spectrometry (SIMS) confirmed an effective boron doping concentration of 2 × 1018 cm−3 and a doping layer thickness of 240 nm. Building upon this, a diamond Metal Oxide Semiconductor Field Effect Transistor (MOSFET) featuring a boron-doped channel was fabricated with a key innovation: the source/drain ohmic contacts were formed directly on a hydrogen-terminated (CH) diamond surface, instead of the boron-doped layer itself. This approach leveraged the inherent non-pinning property and favorable surface conduction of the CH surface to achieve low specific contact resistivity (2.23 × 10−5 Ω·cm2). Furthermore, device series resistance was minimized by reducing gate-source and gate-drain distances to 1 μm. With optimized contact, the BDD MOSFETs achieved a maximum drain current density (IDmax) of −3.6 mA/mm and a peak transconductance (gm,max) of 755 μS/mm. Both key electrical metrics are improved, placing this device at the good performance level among analogous devices with boron-doped bulk-conductive channels. Additionally, a relatively low threshold voltage of 2.6 V was attained, attributed to the thin boron-doped channel. These results significantly surpass previous benchmarks for BDD channel MOSFETs and validate the effectiveness of combining the bulk-doped diamond channels with the low-contact-resistance advantage of hydrogen-terminated surface contacts. This hybrid approach provides a promising new pathway for optimizing high-performance bulk-doped diamond MOSFETs.

In this work, a temperature sensor based on multiheterostructure GaN p-i-n diode with a turn-on voltage (V (on) ) of 4.25 V and a high I (on) /I (off )ratio over 1 & times;10(7) is demonstrated. The fabricated GaN p-i-n diode shows a high-temperature sensitivity of 3.63 mV/K at a low forward current of 1 & times;10(-6) A. The wave functions of electrons and holes are modulated by the inserted InGaN quantum well, and a peak recombination rate of 1.93 & times;10(24) cm( -3)& sdot;s(-1 )with a forward current of 1 & times;10(-6) A is obtained by TCAD. The zero-temperature coefficient (ZTC) point is 5.1 V measured at various temperatures. Meanwhile, the reverse I - V characteristics also present a temperature-dependent behavior with a temperature sensitivity of 8.61 mA/K at a reverse biased voltage of -5 V.

The well known Disc-type magnetorheological finishing (DMRF) has damage-free advantage due to “surface contact” during polishing process. It has got more attention from integrated circuit (IC) industry to obtain wafer-level ultra-smooth planarization and other fields requiring ultra-precise surface processing. However, conventional DMRF configurations exhibiting unstable material removal rate (MRR) which constrain their application, one reason is the variation of the linear speed of the disc polishing surface, the another is evaporation of water in magnetorheological polishing fluid (MRPF) during polishing. To obtain stable material removal rate (MRR), a kind of reciprocating-disc-type magnetorheological finishing (RDMRF) equipment is designed and practiced in our experiment, and the effect factors contributing to drift in removal-function accuracy are identified and discussed, including influence of time. MRPF with sodium-hexametaphosphate (SHAMP) and vapor-deposited silica was used in polishing, and the results showed that the shear stress rises by 47% and sedimentation rate falls by 57% compared with pure magnetorheological fluid. Using this MRPF can achieve a surface roughness of Sa 1.562 nm on workpieces. A Preston-type model integrating workpiece elastic modulus and magnetic-field gradient is established. In order to avoid instability caused by temperature and evaporation, a magnetically actuated recovery loop was constructed to provide on-the-fly replenishment and continuous agitation of the MR fluid. With this loop engaged, the material-removal-rate drift was suppressed to < 8% over 180 min and the areal roughness Sa converged to 1.519 nm. Deviation is caused by minute fluctuations in the composition of the slurry during the polishing process. This reveals the root cause limiting the stability of removal and further improvement in surface quality.

The resonant switched-capacitor (SC) converters have been demonstrated to avoid capacitor current spike and achieve soft switching, to have high reliability and high efficiency. However, the power density is reduced due to the presence of discrete resonant inductors. To address the issue, this work presents an integration method of resonant inductors for the two-phase resonant SC converters by using printed circuit board (PCB) copper traces. The proposed integration method is based on the direct coupling theory, in which the PCB trace coupling of two resonant SC converters in phase can reduce the PCB trace length and copper loss. More importantly, the core loss of discrete inductors can be eliminated. This proposed method can not only improve the light-load efficiency and power density but also reduce the cost of the discrete inductors. Two 240-W gallium nitride (GaN)-based experiment prototypes based on discrete inductors and proposed integrated PCB trace inductors are tested and compared to validate the effectiveness of the proposed integration method. Experimental results demonstrate that the prototype with PCB trace inductors can achieve higher light-load efficiency and power density.

Diamond holds significant application potential in microwave and deep-space observation windows due to its exceptionally low dielectric loss. This study aims to systematically investigate the key factors influencing the dielectric loss tangent (tan delta) of single-crystal diamond (SCD) and to establish a relationship between its dielectric properties and material characteristics. To this end, dielectric properties of SCD samples synthesized using microwave plasma chemical vapor deposition (MPCVD) systems under different growth conditions are measured. A comprehensive material characterization is carried out using birefringence microscopy, Raman spectroscopy, photoluminescence, and X-ray diffraction to analyze crystal quality, defect distribution, and strain. The experimental results show that the measured tan delta values of the SCD samples all reach a minimum value of 4.94 & times;10(-5). Detailed analysis reveals that the dielectric loss in SCD is attributed to a combination of factors: the density and distribution of internal defects (e.g., vacancies and impurities), the presence of internal growth sectors and boundaries, and phonon polarization losses induced by lattice vibrations under an external electric field. It is conclusively identified that defect density is the predominant factor governing dielectric loss. Furthermore, this study demonstrates that as the test frequency increases, contributions from defect polarization and interfacial polarization at sector boundaries become more pronounced, resulting in higher overall loss. Interestingly, it is found that some periodic defect structures can partially suppress the phonon-polarization related loss mechanism, thus helping to reduce the tan delta values in some samples. In summary, this work elucidates the multi-faceted origins of dielectric losses in SCD and provides valuable insights and methodological frameworks for guiding the synthesis and processing of diamond crystals with further enhanced dielectric properties, suitable for advanced microwave and terahertz applications.

Low-dislocation GaN epitaxy on flat sapphire remains challenging when sputtered AlN is used as the nucleation layer because the near-surface state of sputtered AlN can limit subsequent GaN nucleation and coalescence. Here, we introduce Al-ion pretreatment as a pre-growth interface-engineering strategy for sputtered AlN on flat sapphire. With an optimized implantation dose, the GaN mosaic structure is markedly improved. The total threading dislocation density is reduced by 50.5% relative to the conventional substrate. X-ray photoelectron spectroscopy indicates implantation-induced reorganization of the oxygen-related near-surface bonding environment, resulting in a more uniform AlN-like surface for subsequent GaN. Ultraviolet light-emitting diodes grown on the optimized templates also exhibit improved electrical and optical performance. These results demonstrate Al-ion pretreatment as a practical route for low-dislocation GaN epitaxy on sputtered-AlN/flat-sapphire templates.

For heteroepitaxial single-crystal diamond growth, iridium is recognized as the optimal nucleation layer due to its unique carbon-saturated precipitation mechanism that facilitates the formation of highly oriented and dense diamond nuclei. This study employed magnetron sputtering to deposit iridium on (11-20) a-plane sapphire substrates, systematically investigating the effects of deposition temperature, sputtering power, and rapid high-temperature annealing on the orientation, surface morphology, and film quality of Ir. Experimental results demonstrated that (100)-oriented Ir films are successfully achieved at a deposition temperature of 780 degrees C with 125 W sputtering power. Subsequent rapid thermal annealing at 1000 degrees C significantly improved the crystalline quality, evidenced by the reduction of FWHM for Ir (002) XRD rocking curve from 436 to 323 arcsec. TEM analysis confirmed the single-crystal nature of Ir films with minimal lattice strain. This achievement of high-quality Ir films establishes a crucial foundation for optimizing the quality of subsequent heteroepitaxial single-crystal diamond growth. The fabrication of high-quality, highly-oriented iridium films serves as an essential prerequisite for the successful nucleation and growth of high-quality heteroepitaxial diamond. This study demonstrates the deposition of Ir on 2-inch sapphire, thereby representing a critical step toward the realization of heteroepitaxial single-crystal diamond at the 2-inch scale and beyond.

This work reports the first demonstration of reverse blocking $\mathrm{n}-\text{Ga}_{2} \mathrm{O}_{3}$ transistor by constructing $\mathrm{p}-\text{NiO}/\mathrm{n}-\text{Ga}_{2} \mathrm{O}_{3}$ double super-junction (DSJ) MOS junction-FETs (DSJ-MOSJFETs). The DSJ-MOSJFET is beneficial for boosting on-state performance, leading to a large gate swing of 9.5 V and low specific on-resistance ($\mathrm{R}_{\text{on}, \text{sp}}$) of $5.67 \mathrm{m} \Omega \cdot \text{cm}^{2}$. Meanwhile, DSJ technique also enhanced the breakdown voltage (BV) under the charge balance condition, resulting in a BV of 2.4 kV at gate-to-p-NiO spacing (LGP) of $4 \mu \mathrm{m}$. Thus, the average electric field (EAV) is pushed to be 6.1 MV/cm and the $\text{BV}^{2}/\mathrm{R}_{\text{on, sp}}$ power-figure of merit (P-FOM) is yielded to be over 1 GW/cm2. The repeated measurement and stress tests with both shift in VTH less than 0.1 V illustrate the strong stability for this work. Combined with the both forward and reverse BV delivered to be $>8 \text{kV}$, this work shows the great promise for future high-power and high-voltage power conversion applications.

As one of the critical materials for ultra-high-voltage power devices, beta-gallium oxide (beta-Ga2O3) faces significant reliability challenges. Under the coupled effects of repeated electrical stress and high-temperature thermal fields, the stability of this material directly determines the reliability of power devices under extreme service conditions. However, to date, atomic-scale real-time observations and mechanistic explanations of the failure process of this material under coupled electro-thermal fields remain lacking. In this study, using in situ transmission electron microscopy (in situ TEM) under coupled thermal-electrical field (500 degrees C and 1 V bias), we directly observed the anisotropic failure of beta-Ga2O3 along low-index planes such as (200). Controlled decoupling experiments confirm that the electric field serves as the key driver in initiating and guiding this anisotropic melting process. Moreover, electro-thermal stress markedly accelerates the failure, increasing the melting rate from 1.145 to 4.937 nm(2)/s. By combining experimental observations with theoretical analysis, we establish a complete physical chain in which the synergistic effect of the electric field and the material's intrinsic anisotropy drives external field-induced defect generation and migration, ultimately leading to the anisotropic failure of beta-Ga2O3. This work not only provides direct evidence for understanding the failure behavior of beta-Ga2O3 under extreme operating conditions, but also offers crucial design guidance for developing highly reliable high-voltage power devices.

In this work, N-ion implantation pretreatment was introduced into sapphire substrates with sputtered AlN to improve the crystal quality and conductivity of GaN p-channel heterostructures. The effects of different N-ion implantation doses on the material quality and electrical properties of GaN p-channel heterostructures were investigated. Compared with the conventional substrate, the ion-implanted substrates reduced the threading dislocation density and improved the surface morphology. At an implantation dose of 1 × 1012 cm-2, the p-channel heterostructure shows a 26.7% reduction in dislocation density. The sheet hole density increases by 20.0%, while the sheet resistance decreases by 10.9%. These results indicate that N-ion implantation pretreatment is an effective route to improve the conductivity of GaN p-channel heterostructures for future p-FET applications.

In this work, AlGaN/GaN reverse conduction HEMTs (RC-HEMTs) integrated with anti-parallel Schottky barrier diodes (SBDs) are demonstrated. Benefiting from the idealized Schottky interface of AlGaN/GaN SBDs with recessed anode, which enables direct contact between GaN channel and anode metal, low reverse turn-on voltage (VR-T) of -0.75 V and high I-ON/I-OFF ratio of 8.5 & times; 10(7) are obtained. Based on the randomly measured 100 RC-HEMTs with L-GD of 15 mu m, ultra-high VR-T uniformity with standard deviation of 18 mV and forward on-resistance (R-ON) uniformity with standard deviation of 0.3 Omega mm are calculated, respectively. Furthermore, the breakdown voltage of the fabricated AlGaN/GaN RC-HEMT with a 30-mu m L-GD can reach 2.7 kV, which shows great promise for medium-voltage power applications.

In this letter,we demonstrate the effect of γ irradiation on the lateral AlGaN/GaN Schottky barrier diodes(SBDs)with self-terminated recessed anode structure and low work-function metal tungsten(W)as anode.For a comprehensive evaluation of the radiation-resistance performance of the device,the total dose of γ irradiation is up to 100 kGy with irradiation time of 20 h.Attributed to the barrier lowering effect of the W/GaN interface induced by γ irradiation observed in the experiment,the extracted turn-on voltage(VON)defined at anode forward current of 1 mA decreases from 0.47 to 0.43 V.Meanwhile,benefit-ing from the reinforced Schottky interface treated by post-anode-annealing,a high breakdown voltage(BV)of 1.75 kV is obtained for the γ-irradiated AlGaN/GaN SBD,which shows the promising application for the deep-space radiation environ-ment and promotes the development of radiation-resistance research for GaN SBDs.

In this work, current-collapse suppressed highperformance AlGaN/GaN Schottky barrier diodes (SBDs) with excellent reverse blocking characteristics are demonstrated. Benefiting from the modulated electric field via an optimized $6-\mu \mathrm{m}$ PN junction termination and the in-situ NH3 plasma treated GaN passivation layer at the active region, the fabricated AlGaN/GaN SBD with $100-\mu \mathrm{m}$ anode-to-cathode distance ($L_{\text{AC}}$) achieves a high breakdown voltage over -10 kV and a high Baliga's figure-of-merit (FOM) over 2.1 $\text{GW} / \text{cm}^{2}$. Meanwhile, compared to the static characteristics, the degradation of dynamic differential on-resistance (Ron, dyn) and dynamic turn-on voltage ($V_{O N, d y n}$) are extracted to be 19.1 % and 3.7 %, respectively, after a 1000 -s-long bias test at -3 kV. The impressively high breakdown and dynamic performance show great potential for next-generation medium-and-high voltage powerelectronic applications.

In this work, a high-performance AlGaN-channel Schottky barrier diode with high breakdown voltage of 2.23 kV defined at anode leakage current of 1 μA and high power figure-of-merit of 614 MW/cm2 is demonstrated. Anode voltage (VA) with a clear linear relationship as a function of temperature from 300 to 525 K shows great potential for temperature sensors, and maximum temperature sensitivity of 2.0 mV/K at anode current density (IA) of 6.28 × 10−8 A is obtained, satisfying the low power consumption requirement. Meanwhile, the corresponding temperature sensitivity of ln(–I) vs temperature at a fixed VA of –15 V is 5.0 mA/K, and the suppressed temperature sensitivity at reverse bias is attributed to the energy-band modulated Schottky barrier height of AlGaN-channel M/S interface, which is vital for high-temperature and high-power applications.

In the process of epitaxial growth of alpha-Ga2O3, high density dislocations influence the quality of materials and the performance of devices. In this work, the effects of electron beam irradiation in transmission electron microscope (TEM) on different kinds of defects in alpha-Ga2O3 were studied. For dislocations, in situ dark field images based on different diffraction vectors and high-resolution TEM images both indicate that after electron beam irradiation (2500 e/& Aring;(2)s), the repair phenomenon of dislocations with a Burgers vector of 1/3 < 1123 > and 1/3 < 1100 > is observed. With respect to larger size defects, the nano pit (8 x 5 nm(2))was repaired to a large extent along ( 1014) after irradiation by an electron beam of 2500 e/& Aring;(2)s for 39 min. Under electron beam irradiation with the same intensity for 42 min, the nanopore (10 x 9 nm(2)) was partially repaired along (0006) due to the more severe damage. This discovery provides a method to reduce the defects in two-dimensional alpha-Ga2O3, which is conducive to the further understanding of the properties of two-dimensional alpha-Ga2O3 and the development of a variety of devices based on it. At the same time, the potential impact of electron beam irradiation needs to be considered in the process of device manufacturing and the reliability of devices in space. On the contrary, this work also provides positive guidance for defect repair in other semiconductor materials that may be sensitive to electron beam irradiation.

Thermal accumulation under high output power density is one of the key bottlenecks faced by GaN-based power devices.The nanocrystalline diamond(NCD)passivation layer strategy plays a crucial role in improving heat dissipation in high-power GaN devices,while the existing studies focus on GaN-based HEMT.In this study,nanocrystalline diamond films with a thickness of 380-450 nm are grown on Si-based AlGaN/GaN heterostructure materials using a microwave plasma chemical vapor deposition(MPCVD)system.Consequently,lateral Schottky barrier diode devices with NCD passivation are fabricated,and their electrical and thermal properties are investigated.The results show that the DC forward characteristics of the NCD passivated diodes are essentially the same as those of devices without NCD passivation.Moreover,dynamic voltage tests indicate that the NCD passivation layer significantly mitigates currentcollapse in GaN devices at high frequencies.Under a-20 V DC bias and a pulse voltage of 2.5 V,the current density degradation of NCD passivated devices is only 2.6％,whereas devices without diamond passivation almost completely degrade.Thermal imaging microscopy under varying DC power levels shows that thermal failure occurs at an output power density of approximately 4 W/mm for conventional devices,while NCD passivated devices can reach around 7.5 W/mm.The electrical degradation behaviour of NCD passivated device is also tested under long-time reverse bias.This work demonstrates for the first time the application of nanocrystalline diamond passivation to thermal management of GaN-based power diodes,and clearly demonstrates the potential of this strategy in non-HEMT power device applications.

Schottky-type p-GaN gate HEMTs with a low forward bias gate breakdown voltage V G-BD are vulnerable to failures during switching. In this work, high-performance MIM/p-GaN gate HEMTs with a TiN/Al 2 O 3 /TiN (30/3/40 nm) MIM structure on top of p-GaN layer are proposed. Compared to the conventional Schottky-type reference, the MIM/p-GaN gate structure successfully promotes the V G-BD from 11.4 to 14.1 V and the maximum applicable gate voltage V G-max from 5.1 to 7.0 V corresponding to a lifetime of 10 years at the failure of 1%. Benefiting from the 3-nm ultra-thin Al 2 O 3 layer and the MIM structure, trapping effect is avoided. Neither significant degradation of static nor dynamic characteristics of the proposed devices are observed. The developed MIM/p-GaN gate HEMTs present great potentials for future power conversion applications.