Abstract This work proposes a novel double-gate (DG) junctionless (JL) capacitorless dynamic random access memory (1T-DRAM) by combining a trench-isolated channel and a high-k gate dielectric (TiO2) to improve the performance metrics of the memory cell. The trench-isolated channel architecture design, formed by incorporating SiO2 filled comb structures within the silicon body, improves charge confinement and reduces recombination, thereby increasing retention time (Tret) and sense margin (SM). Comprehesive TCAD simulation results show that significant improvements in retention and sensing characteristics. The device achieves a Tret of ∼ 179 ms and a SM of ∼14.84 μA/μm at 27 ◦C. Also, with increase in temperature of 85 ◦C, it maintains a Tret of ∼10 ms and an SM of ∼10.27 μA/μm, indicating robust thermal stability. This enhanced electrostatic integrity of the DG JL structure further reduces short channel effects (SCEs) and improves data reliability.
Abstract We calculate the radiative and Auger recombination rates in polar c-plane and nonpolar m-plane InxGa1-xN/GaN quantum wells with different alloy compositions x ranging from 0.1 to 0.5. The calculation is based on a full-zone electronic structure description obtained with the linear combination of first-principles (density functional theory with GW corrections) bulk bands approach. The results show that both the radiative and Auger recombination coefficients are higher in nonpolar quantum wells for all alloy compositions studied. We find that the competition between radiative and Auger recombination cannot explain the experimental findings on the improved performance of m-plane quantum well light emitters, suggesting a significant contribution from another efficiency reduction mechanism, likely not purely intrinsic but related to carrier transport and confinement.
Abstract A novel 1200 V planar split-gate 4H-SiC MOSFET with an enlarged grounded P⁺-shielding and local N-compensation (PSC-MOS) is proposed and investigated using TCAD simulations for enhanced drain-induced barrier lowering (DIBL) suppression and switching performance. By introducing the N-compensation region adjacent to the P⁺ shield within the JFET region, depletion-induced current-path constriction is alleviated, thereby strengthening drain-to-channel electrostatic shielding and reducing gate–drain capacitive coupling without an excessive conduction penalty. The N-compensation parameters are optimized by considering the trade-offs among DIBL suppression, conduction capability, and breakdown performance. Demonstrated by TCAD simulation results, compared with the uncompensated LPS-MOS employing the same enlarged P⁺ shield, the optimized PSC-MOS reduces the specific on-resistance (Ron,sp) and switching loss (Esw) by 39.1% and 23.2%, while increasing the Baliga figure of merit (BFoM) by 58.7%. Compared with the conventional P⁺-shielded MOSFET (PS-MOS), it reduces the DIBL coefficient (kDIBL) by 17.1%, the high-frequency figure of merit (HF-FoM, Ron,sp × Qgd) by 9.7%, and Esw by 3.2%. These results demonstrate an improved balance among electrostatic control, conduction capability and switching performance.
Abstract This paper proposes a novel enhancement-mode gallium nitride high electron mobility transistor (GaN HEMT), featuring a step-graded doping p-GaN buried layer (TPBL-HEMT), to significantly enhance its short-circuit (SC) capability. The buried layer architecture, comprising a highly-doped source anchor, a moderately-doped main shielding region, and a lightly-doped soft termination, effectively decouples SC current suppression from electric field shaping. TCAD simulation results validate that the source anchor effectively clamps the SC current, while the soft termination modulates the drain-side electric field, thereby reducing its peak. The optimized device achieves a great SC withstand time of 1.58 µ s under a 400 V bus voltage, which is 246% longer than that of the traditional device conventional HEMT. This work presents a highly promising engineering solution for designing robust and reliable GaN power devices.
Abstract With advances in AI and the widespread adoption of NAND Flash technology imposing increasingly stringent performance requirements, conventional erase was unable to provide precise erasing in NAND Flash storage systems. This work proposes a novel cell-level erase scheme called hole pool (HP) erase by integrating the cell-level voltage scheme with the source acceptor doping structure. The technique was evaluated in 3D NAND Flash structures with different numbers of layers, in which stable electric field and charge variation characteristics were obtained, thereby demonstrating its feasibility and applicability to highly stacked architectures. The results showed that the HP erase successfully enabled precise cell-level erase in 3D NAND Flash, which reduced erase operations in unselected cells. Additionally, the optimized erase scheme lowered the required erase voltage, which provided a more efficient approach for erase operations. This highlights a promising direction for the future development of erase technology in highly stacked NAND Flash architectures.
Abstract Accurate band offsets are essential for predictive continuum modeling of nanostructures such as quantum wells and quantum dots formed in strained Si/Si 1 − x Ge x and Ge/Si 1 − x Ge x heterostructures. Experimental offset data for these systems remain sparse away from endpoint compositions, which makes composition-dependent design difficult. We use atomistic, first-principles density functional theory to compute valence- and conduction-band offsets across the full range 0 ⩽ x ⩽ 1 . Random alloying is treated with special quasirandom structures, interface lineup terms are extracted from macroscopically averaged local Kohn–Sham potentials in thick periodic superlattices, valence-band spin–orbit coupling is included through species-resolved Mulliken weights, and conduction-band edges are refined using the screened hybrid Heyd–Scuseria–Ernzerhof functional. The resulting offsets show pronounced composition nonlinearity beyond the linear models explored in previous works, agree with experimental benchmarks, and reproduce the high-Ge slope change in the relaxed-alloy band gap. Analytic fitting expressions are provided for direct use in simulations, facilitating practical design of modern quantum technology devices.
Abstract The turn-on speed of gate turn-off (GTO) is a critical performance metric in nanosecond pulse applications. This work analyzes the super-injection effect in heterojunctions and proposes a fast-turn-on SiC heterogeneous GTO thyristor to overcome the insufficient response speed of conventional SiC P-GTOs. Through analysis of asymmetric electron and hole potential barriers, physical insights into injection modulation are revealed numerically. The R on,diff of a diamond/SiC heterojunction is 2.4 mΩ cm 2 at 200 A cm −2 , which is 22% lower than that of a SiC homogeneous junction. The hole injection efficiency is raised to above 0.99. Consequently, a diamond/SiC heterogeneous GTO (DH-GTO) raises the accumulated carrier density by about two times via the super-injection effect. The current rise time is shortened to a mere 15 ns under a 8 kV/4 kA and 100 ns pulse. The design achieves a 152% theoretical improvement in d i /d t with wide doping tolerance, resulting in a quasi-rectangular pulse waveform. Compared with homogeneous and other heterogeneous GTOs, the DH-GTO demonstrates the most promising static and pulsed performance along with broad doping tolerance. These results provide a novel optimization strategy for improving the turn-on transient of SiC GTOs, thereby advancing nanosecond power pulse technology.
Abstract Using admittance spectroscopy, the dispersive transport mobilities of electrons and holes were simultaneously obtained from the distinct carrier transit times ( τ t ) in the molecular beam epitaxy-grown GaAs/Al x Ga 1− x As heterojunction-based solar cell device. The negative capacitance effect was attributed to the delayed response of injected carriers under forward-bias space-charge-limited conditions, where different electron- and hole-related transit times appear in different frequency regions of the C -log f characteristics when V F exceeds approximately 1.2 V. For V F < 1.2 V, i.e. below the built-in voltage ( V bi ), the activation energy determined from the current density–voltage ( J – V ) characteristics was attributed to the hole energy barrier associated with the valence-band offset between p + –Al 0 . 82 Ga 0 . 18 As and p + –GaAs layers. This assignment is consistent with literature-based theoretical band-offset estimates and is also supported by the photoconductivity measurements.
Abstract To improve the threshold voltage ( V th ) of the enhanced GaN HEMT device, mitigate the risk of false turn–on due to crosstalk between high-side and low-side HEMTs, and decouple the reverse turn-on voltage ( V RT ) from the gate–source voltage to minimize losses during reverse conduction, this paper introduces a decoupled dual-gate HEMT (DDG-HEMT) device. The DDG-HEMT features a decoupled auxiliary gate on the extended p–GaN region on the source side and employs a clamping mechanism between the main gate and the source, resulting in a substantial increase in the V th . Based on equivalent circuit model and band diagram analysis, the physical mechanisms of DDG-HEMT are clarified. The research findings indicate that as the thickness of the extended p-GaN region on the source side of the DDG-HEMT increases from 9 nm to 15 nm, the V th rises from 2.80 V to 4.79 V. Compared to the 1.52 V V th of C–HEMT, increased by 84.2% and 215.1% respectively. Simultaneously, the transconductance of DDG-HEMT improved by approximately 60% compared to the 40.5 mS mm −1 of C–HEMT devices. Additionally, this paper characterizes dynamic parameters, including gate capacitance and gate charge. The results show that, with the extended p–GaN region thickness of 10 nm on the source side, the gate capacitance measures 384.2 nF cm 2 , and the gate charge is 4.2 nC. Notably, the DDG-HEMT decouples the V RT from the gate–source voltage, allowing for a high V th while stabilizing the V RT at 1.20 V across varying gate–source voltages. In practical applications, this capability significantly reduces losses during reverse freewheeling, thereby enhancing overall system efficiency.
Abstract Two-dimensional electron gases (2DEGs) play a central role in a wide range of electronic components. A thorough understanding of mobility-limiting scattering mechanisms is therefore crucial for the design of high-performance devices. In particular, with continuing device miniaturization, scattering processes such as interface roughness (IFR) scattering increasingly influence the mobility of more confined 2DEGs. This paper reviews the theoretical treatment of the essential scattering mechanisms within the effective mass theory, along with the solution of the Boltzmann transport equation via linearization and the momentum relaxation time approximation. An AlN/GaN high-electron-mobility transistor (HEMT) with experimentally measured mobility is used to evaluate multiple IFR scattering models and to examine the effect of static free-carrier screening on polar optical phonon (POP) scattering. Furthermore, to facilitate reproducibility, the inverse momentum relaxation time of each individual scattering mechanism is presented for a 2DEG density of 1×10 13 cm −2 . Finally, recent theoretical predictions of mobility enhancement in AlN/GaN HEMTs are highlighted.
Abstract A novel wide-bandgap semiconductor heterostructure, diamond/gallium oxide (Ga 2 O 3 ), demonstrates significant potential in the fields of optoelectronic devices, power electronic devices, and radiation detection. The synergistic combination of the materials’ outstanding features, including diamond’s relatively mature p-type doping technology and exceptional thermal conductivity, along with Ga 2 O 3 ’s n-type conductivity and broad ultraviolet (UV) spectral response range, enhances the performance and application scope of photodetectors. This review presents recent advancements in diamond/Ga 2 O 3 heterojunction devices, covering progress in band engineering, interface design, and strategies for optimizing device performance. Furthermore, it analyzes potential applications of diamond/Ga 2 O 3 photodetectors in imaging systems, self-powered sensing, and extreme environment monitoring. Future research prioritizes interface passivation, defect engineering, and scalable fabrication techniques to facilitate the practical application of this material system in deep UV photonics and intelligent sensing technologies.
Abstract In this study, a van der Waals heterostructure was created by combining molybdenum ditelluride (MoTe 2 ) with molybdenum disulfide (MoS 2 ) on flexible polyimide (PI) substrates. The aim was to tackle challenges in flexible photodetection applications. The device operated self-powered across visible to near-infrared wavelengths without external bias, leveraging the strong built-in electric field resulting from the type-II band alignment between p -type MoTe 2 and n -type MoS 2 . It achieved an on/off ratio of 2.25 × 10 4 at 640 nm and maintained a high responsivity of 18 mA W −1 under 1064 nm laser illumination. Optoelectronic performance was systematically adjusted through uniaxial tensile strain. The photocurrent response showed a non-monotonic behavior with strain, initially increasing and then decreasing, with a roughly 31.8% boost in responsivity at a critical strain of 0.50%. This modulation in performance was attributed to the interplay between strain-induced bandgap reduction and band structure evolution. Additionally, the flexible device exhibited consistent photocurrent after 1000 consecutive bending cycles, indicating strong mechanical reliability. This study paves the way for dynamically manipulating the band structure of two-dimensional heterojunctions through strain, opening avenues for advanced, wearable, flexible self-powered photonic devices.
Abstract Intensity-modulated proton therapy (IMPT) employs proton radiation rather than conventional x-rays to treat cancerous tumors. This approach offers significant advantages by minimizing the radiation exposure of surrounding healthy tissue, leading to improved patient outcomes and reduced side effects compared to traditional x-ray therapy. To ensure patient safety, each treatment plan must be experimentally validated before clinical implementation. However, current dosimetry devices face limitations in performing angled beam measurements and obtaining multi-depth assessments, both of which are essential for verifying IMPT treatment plans. In this study, the performance of a β -Ga 2 O 3 -based metal–semiconductor–metal detector with a low-noise amplifier has been studied and evaluated under various proton radiation doses and energy levels delivered by a MEVION S250i proton accelerator. The detector’s performance was also compared with that of an ionization chamber. The β -Ga 2 O 3 detector exhibited a linear response with proton dose for single-spot irradiations, and its response to varying proton energies closely matched both the ion chamber data and simulated dose distributions. These findings highlight the potential of β -Ga 2 O 3 -based detectors as robust dosimetry devices for IMPT applications.
Abstract Gallium oxide is an emerging ultrawide-bandgap semiconductor with great potential for power electronics, yet the growth of its large crystals remains limited by defect and yield challenges. In this study, a coupled thermal–mechanical finite element model is established to analyze thermal field optimization and stress distribution in gallium oxide crystals grown by the vertical Bridgman method. The results show that multiheater configurations reduce power consumption and enhance radial uniformity in the furnace, but radiative shielding by the intermediate insulation layer increases axial gradients, confirming radiation as the dominant heat transfer mechanism. Stress analysis reveals that stress concentrates mainly in the shoulder and constant-diameter growth regions due to crystal and the crucible, while larger shoulder angles effectively alleviate stress in the process of single-crystal growth. These findings highlight the importance of coordinated heater–insulation optimization and crucible design, providing guidance for high-quality, large-diameter gallium oxide crystal growth.
Abstract Steep-slope transistors are essential for emerging ultra-low-power electronic systems operating at reduced supply voltages. However, conventional silicon tunnel field-effect transistors (TFETs) suffer from poor tunneling probability at the source–channel junction, which limits ON-state current. In this work, a Si 0 . 5 Ge 0 . 5 source graded-channel ferroelectric TFET (SiGe-GC-Fe-TFET) is introduced and comprehensively investigated using calibrated Silvaco ATLAS TCAD simulations. The device integrates SiGe source bandgap engineering, graded channel electrostatic modulation, and a ferroelectric Si:HfO 2 gate stack to simultaneously enhance tunneling efficiency and gate controllability. The optimized structure confirms enhanced switching performance with a steeper point subthreshold swing of 23.8 mV dec −1 at V DD = 0.5 V, a high ON-state current of 3.95 × 10 −1 A, and an ON–OFF current ratio of ∼1.2 × 10 10 . The proposed device further exhibits improved analog/RF behavior with a cut-off frequency of ∼ 15 GHz, gain-bandwidth product of ∼33 GHz, and reduced Miller capacitance, enabling enhanced high-frequency response. Linearity analysis shows improved distortion immunity with VIP3≈3 V and IMD3≈−2 dBm, while noise analysis reveals significantly suppressed current and voltage noise spectral densities. Finally, inverter circuit implementation confirms enhanced static noise margin and reduced dynamic overshoot. These results demonstrate that the integrated effect of SiGe heterostructure engineering, graded channel design, and ferroelectric negative capacitance provides an effective pathway toward high-performance, energy-efficient TFETs for next-generation low-power mixed-signal and high-end RF applications.
Abstract In this study, microplastic (MP) particles were used in the production of p–n junction devices, marking an important step in the recycling of these particles, which cause environmental pollution. The characteristic features of microplastics formed during the washing of textile materials in the first stage of the device formation were examined. Energy Dispersive Spectrum (EDS) analyses showed that the examined microplastic samples contained a rich Boron (B) content in their structures, originating from cleaning materials. X-ray diffraction (XRD) analysis revealed a mixed-phase structure with both crystalline and amorphous components, supporting the presence of boron-based compounds such as B₂O₃, H₃BO₃, and B₄C within the microplastic matrix. Optical absorption measurements demonstrated three major absorption bands, which support the presence of boron-based phases. The resistivity of the microplastic film on glass was measured by the four-point probe as 9.36105 -cm in the dark and 9.23105 -cm under illumination (100 mW/cm²). A p–n junction device with In-Ga/MP-derived p-Si/n-Si/Al configuration was successfully fabricated using a UV-assisted photoinduced diffusion method, which eliminates high-temperature processing and potential structural damage. The conductivity type of the MP-derived Si surface was investigated by hot-probe and Hall effect measurements, indicating the formation of p-type conductivity after the UV-assisted photoinduced diffusion process. The characteristic parameters of the device were determined from the current (I )– voltage (V) and capacitance (C)–voltage (V) measurements.. Dark I–V measurements showed that the samples illuminated for 30 and 60 min exhibited clear rectifying behavior characteristic of a p–n junction, whereas the control sample without UV illumination did not show rectification. In addition, capacitance–voltage (C–V) measurements revealed relatively high acceptor concentrations on the order of 1017 cm-3, which increased with prolonged UV illumination, suggesting enhanced boron incorporation into the Si surface.
Abstract Two-dimensional (2D) materials have attracted tremendous attention in recent years due to their unique optical and electrical properties and have shown great potential for high-speed optoelectronic devices. Hybrid-integration 2D materials on photonic integrated circuits (PICs) open new avenues for on-chip photonics for providing a CMOS process compatible, platform-independent and more universal solution for optoelectronic conversion. Especially, they can offer supplementary functions for current PIC platforms such as in mid-infrared wavelength band or on novel dielectric platforms. This paper reviews the recent progress of hybrid-integrated 2D materials optoelectronic devices, mainly focusing on high-speed modulators and photodetectors. Firstly, the state-of-the-art waveguide-integrated 2D materials modulators are reviewed, including their working mechanisms and key figure of merits. Secondly, the fundamental physical mechanisms of photodetectors are summarized and the recent developments of waveguide-integrated 2D materials photodetectors are reviewed, notably concentrating on novel waveguide structures for enhancing the light matter interactions. Finally, the challenges and outlook of hybrid integrated 2D materials optoelectronic devices are concluded and discussed.
