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.

Deep space exploration demands high-performance particle detectors capable of withstanding complex and harsh environments, including extreme temperature fluctuations and intense radiation. Conventional silicon-based semiconductor detectors are prone to degradation under such extreme conditions, falling short of mission requirements. To address this issue, we present a novel diamond radiation detector utilizing a composite electrode structure and aerospace-grade packaging materials. Fabricated with high-purity singlecrystal diamond, the detector features a Ti/Pt/Au composite electrode that significantly enhances adhesion strength and bonding reliability. This design achieves a 100% first-pass success rate for 25-mu m gold wire bonding, with an average bond pull strength of 9.8 g. The use of aerospace-grade FR4 packaging with a through-hole structure allows the sensitive area to be directly exposed to the space environment while supporting multichip stacking and back-end sensor integration for versatile mission profiles. Performance tests and space environment adaptability experiments demonstrate a charge collection efficiency (CCE) exceeding 90% at a 200-V bias, an energy resolution better than 2%, a dark current below 50 pA at 250 V, and tolerance to a total gamma-irradiation dose of 10 000 krad without performance degradation. The detector also maintains excellent current characteristics and spectral response at 120 degrees C. This work overcomes the operational limits of traditional semiconductor detectors and advances the application of novel diamond detectors in deep space exploration.

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.

Currently, hydrogen-terminated (C-H) diamond surfaces are typically fabricated by directly exposing the diamond to a hydrogen-based microwave plasma, a method referred to as plasma-contact hydrogenation. This work presents an alternative non-plasma-contact hydrogenation approach, where a sacrificial SiO2 layer grown on (001) diamond is employed. During microwave plasma chemical vapor deposition (MPCVD), the plasma does not directly interact with the diamond surface; instead, atomic hydrogen diffuses through the SiO2 layer at elevated temperatures to form the C-H diamond. Compositional and morphological analyses reveal that a smooth C-H (001) diamond surface was achieved, accompanied by a small fraction of oxidized Si-terminated (C-Si-O) diamond species, which facilitates subsequent oxide film growth. The fabricated (001) diamond MOSFET with a gate length (L- (G) ) of 4 mu m demonstrates normally on behavior and a maximum drain current density ( I-D_MAX ) exceeding 1 A/mm, outperforming other diamond FETs of comparable L-G. These promising results underscore the potential of the proposed non-plasma-contact hydrogenation technique to advance diamond-based electronic devices and heterojunction technologies.

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.

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.

We report the GaN-based diode avalanche shaper (DAS) employing ultra-small-angle bevel junction termination extension and slanted field plate hybrid edge terminations. Compared with Si and GaAs DASs, the thinner and lightly doped drift layer maintains a uniformly high electric field prior to avalanche, enabling full-region avalanche without impact ionization-wave propagation and yielding over two orders of magnitude higher current density. The GaN DAS delivers a >2.5 kV peak output voltage with a 93 ps rise time and achieves a 4-times bandwidth enhancement from 1.6 to 6.3 GHz. A record peak output power density of 1.68 GW/cm(2) is obtained, exceeding those of Si and GaAs DASs by more than 100 times of magnitude and that of SiC DASs by a factor of 27. These results underscore GaN as a leading wide-bandgap platform for picosecond-class ultrafast DASs and compact, ultra-wideband, high-repetition-rate pulsed power systems.

This work demonstrates a high-performance AlGaN/GaN high-electron-mobility transistor on SiC, featuring an unintentionally doped AlN super back barrier (SBB) and an ultra-thin GaN channel. This structure directly addresses the limitation of conventional Fe- or C-doped buffers, where deep-level dopants induce high trap densities, severe current collapse, and reliability degradation. The AlN SBB/GaN heterointerface provides a large conduction band offset for robust carrier confinement and high intrinsic resistivity for effective leakage suppression. Consequently, the fabricated high-electron-mobility transistors exhibit low off-state leakage, a breakdown field exceeding 2.1 MV cm-1, and minimal current collapse of only 10.87%. At 3.6 GHz, the device delivers a high output power density of 13.58 W mm-1at a 70 V drain bias and achieves a peak power-added efficiency of 73.06% at 40 V. These results underscore the effectiveness of the AlN SBB with an ultra-thin channel in simultaneously enabling high breakdown strength, high power, and high efficiency, providing a promising solution for next-generation RF power applications.

AlN back-barrier thickness physically governs ultrathin-channel GaN high-electron-mobility transistor (HEMT) performance by dictating a competition between material states. At 440 nm, the AlN back barrier effectively relaxes strain while maintaining two-dimensional growth, yielding high mobility and a trap profile favorable for robust short-channel breakdown and high-frequency operation-resulting in f(T)/f(max) = 34.32/70.95 GHz and 69% power-added efficiency at 3.6 GHz. For a thicker 1-mu m layer, three-dimensional island growth with deep-level traps dominates, providing superior vertical blocking to achieve 1.78 kV breakdown voltage for high-voltage operation. By linking the AlN back-barrier thickness to these underlying physical mechanisms, this work establishes a physics-based design framework for deterministically tailoring GaN HEMTs toward high-frequency or high-voltage operation, thereby opening a viable pathway to advance the performance limits of nitride electronics.

Cubic boron nitride (c-BN)/diamond heterostructure provides a new solution to avert the challenging diamond n-type doping and facilitates high two-dimensional carrier density and mobility in diamond field effect transistor (FET). However, the growth of c-BN/diamond system is still difficult at present. In this study, a physics-based analytical model for the 2DEG sheet density and drain current in c-BN/diamond transistors is developed by incorporating the material-specific band structure, electrostatic conditions, and carrier transport properties of the heterostructure into the charge control and transport formulations. The crucial physical effects, such as velocity saturation, channel length modulation, and short-channel effects, are also included. The velocity field-related arguments and structural parameters of the heterostructures are varied to explore the potential performance of c-BN/diamond FETs. Our work proves that the analytical model is comparable to the TCAD simulation results when ua is adopted as − 5.5. The saturation drain current for barrier doping concentration of 2 × 1018 cm−3 is as high as 1270 mA/mm for analytical calculation at gate voltage of 4 V. With more barrier doping involved, the drain current can be further improved to 1367 mA/mm with barrier doping density of 5 × 1018 cm−3. This study provides a basis for the future application of c-BN/diamond FETs in large power and high-temperature electronic device fields.

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.

This letter reports the polycrystalline diamond (PCD) dosimeter with near ideal linearity and high sensitivity to meet the application requirements of medical X-ray dose measurement for low cost, large size, and high performance. The device is fabricated by using hydrogen termination modulation ohmic contact and high-quality materials with preferred (111) and (311) crystal orientation, large grain size and low impurity content. The linearity, specific sensitivity, and current gain obtained from experimental measurements are 0.999, 1.482 mu C center dot Gy(-1 )center dot mm(-3) and 5.76 at 300 V (1V/ mu m), respectively. Furthermore, the signal-to-noise ratio that meets the requirements of International Atomic Energy Agency is greater than 104 at 5 to 300 V, and the current fluctuations under dynamic voltage switch test condition of more than 30 cycle (2 s on-state and 1 s off-state) is only 0.241% at 200 V under dose rate of 6.184 Gy/min. This study indicates that PCD dosimeter fabricated by optimizing contact structure and material properties has a great potential for medical dose measurement.

beta-Ga2O3 is promising for high-voltage and RF devices but challenged by its low thermal conductivity, causing excessive device temperatures. The integration with high-thermal-conductivity materials like diamond and structure optimization are solutions. However, prior simulations often simplified assumptions on Ga2O3 thickness and bulk thermal conductivity. This work employs 3D finite element thermal analysis to investigate beta- Ga2O3-ondiamond cooling strategy, incorporating Ga2O3 and diamond thermal conductivity anisotropy and thickness dependence. We analyze the impact of layer thickness, Ga2O3/diamond interfacial thermal conductance, power density, and double-sided diamond thermal dissipation layers on junction temperature. Results show that Ga2O3 thermal anisotropy is critical for accurate temperature prediction, while diamond anisotropy is negligible. Within a 5 % error margin, the thickness dependence of Ga2O3 thermal conductivity is insignificant with diamond substrate solely, and both the Ga2O3 thickness dependence and its anisotropy can be neglected under doublesided diamond cooling. This study aids thermal management and accurate temperature prediction in Ga2O3/ diamond devices.

The (110) single crystal diamond has certain advantages over the mainstream (100) diamond in the application of electronic devices, but there was rare research on its epitaxy. The growth condition of (110) diamond was optimized, resulting in a methane concentration of 4 % and an oxygen concentration of 0.5 %. Growth of 5 h revealed the dominance of (100) and (111) facet growth in < 110 > epitaxy on top surface with a growth rate of 16.6 mu m/h. Meanwhile, at (110) and (100) substrate sides, the corresponding epi-crystal sides were grown to (100) and (111) surfaces, resulting in a shrinkage of (110) top surface. However, a 100 h growth on a 5 mm x 5 mm substrate led to a crystal with top surface first expanding to 7.03 mm x 8.12 mm and then shrinking, finished with maximum thickness of 3.1 mm and crater-like top surface covered by large ridges with height of similar to 1 mm along <100> direction and polycrystals. A 1-mm-thick (110) diamond plate was cut from the largest expansion part, and showed the width of the X-ray rocking curve much reduced than that of substrate at (110), (100) and (111) planes. This first report of expansion growth of the (110) diamond could provide new insight and way of fabrication of diamond semiconductor materials and devices.

With a dense two-dimensional hole gas (2DHG) p-type conductive layer near the surface, hydrogen-terminated (C–H) diamond metal-oxide-semiconductor field-effect transistors (MOSFETs) have shown typical normally-on operations and high breakdown voltages ( V BR ). Owing to the high MOS interface quality, the oxidized silicon-terminated (C–Si–O) diamond MOSFETs have featured excellent normally-off characteristics, such as high threshold voltage ( V TH ). However, the reported C–Si–O diamond MOSFETs were all exhibited an overlapping-gate structure, and therefore couldn't withstand high voltages. In this work, we demonstrated a novel C–H diamond MOSFET structure with a partial C–Si–O channel to improve the voltage withstand capability of normally-off C–Si–O diamond MOSFETs. The C–H/C–Si–O/C–H channel structure was achieved by forming an entire C–Si–O channel first, and then selectively replacing the C–Si–O channel to the C–H channel by using a SiO 2 mask. As a result, for the fabricated device with a C–Si–O channel length of 2 μm and a gate-to-drain distance ( L GD ) of 11 μm, V TH = -8.6 V and OFF-state V BR = -1376 V have been obtained. These competitive results reveal that the proposed device structure is promising in pushing the normally-off C–Si–O diamond MOSFETs into the high voltage applications.