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Electrical characterization of high k-dielectrics for 4H-SiC MIS devices
摘要： We report promising results regarding the possible use of AlN or Al2O3 as a gate dielectric in 4H-SiC MISFETs. The crystalline AlN ?lms are grown by hot wall metal organic chemical vapor deposition (MOCVD) at 1100 °C. The amorphous Al2O3 ?lms are grown by repeated deposition and subsequent low temperature (200 °C) oxidation of thin Al layers using a hot plate. Our investigation shows a very low density of interface traps at the AlN/4H-SiC and the Al2O3/4H-SiC interface estimated from capacitance-voltage (CV) analysis of MIS capacitors. Current-voltage (IV) analysis shows that the breakdown electric ?eld across the AlN or Al2O3 is ～ 3 MV/cm or ～ 5 MV/cm respectively. By depositing an additional SiO2 layer by plasma enhanced chemical vapor deposition at 300 °C on top of the AlN or Al2O3 layers, it is possible to increase the breakdown voltage of the MIS capacitors signi?cantly without having pronounced impact on the quality of the AlN/SiC or Al2O3/SiC interfaces.
关键词： MIS structure,Interface traps,Al2O3/4H-SiC interface,AlN/4H-SiC interface
更新于2025-11-14 17:28:48
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Spatially Uniform Shallow Trap Distribution in an Ultrathin Organic Transistor
摘要： In organic electronic materials, charge carrier transport is often limited by disorder-induced trap states very close in energy to the ideal band transport states. We directly view the location and impact of these 'shallow' traps on an ultrathin transistor active layer using Kelvin Probe Force Microscopy. As the transistor turns on, dramatic fluctuations in the surface potential of the active channel suddenly arise due to charge trapping and release processes. Importantly, the spatial distribution of rapid fluctuations in surface potential is uniform throughout the active channel. These facts strongly constrain the microscopic origin of shallow charge traps, and associated efforts to optimize the mobility and noise performance baseline in device applications.
关键词： disorder,charge traps,electrical noise,organic electronics
更新于2025-09-23 15:23:52
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Impact of oxide/barrier charge on threshold voltage instabilities in AlGaN/GaN metal-oxide-semiconductor heterostructures
摘要： Threshold voltage instabilities in AlGaN/GaN metal-oxide-semiconductor (MOS) heterostructures were investigated by means of capacitance-voltage (CV) hysteresis measurement and simulations. We focused on the impact of net charge at oxide/semiconductor interface (Qint) on the CV hysteresis. Our simulations suggest that due to different band bending at the interface, any positive or negative Qint with lower density (in the order of 1012 cm?2) results in a presence of relatively shallow unoccupied oxide/barrier interface states in equilibrium. On the other hand, high density of negative Qint (Qint/q ≈ ?1013 cm?2) results in very deep unoccupied interface states, which in turn leads to incomplete electron re-emission during backward CV sweep and thus increased CV hysteresis of the MOS heterostructures compared to previous case. Impact of Qint is illustrated experimentally on MOS heterostructures with Al2O3 gate dielectric grown by metal-organic chemical vapor deposition, showing Qint of ?1.2 × 1013 and +0.5 × 1012 cm?2 for structures with and without post-deposition annealing, respectively. Our results therefore suggest that normally-off AlGaN/GaN MOS heterostructure field-effect transistors featuring high density of negative Qint can be expected to be more susceptible for threshold voltage instabilities compared to normally-on counterparts.
关键词： MOS,Al2O3 gate dielectric,Heterostructure field-effect transistor,Interface traps,AlGaN/GaN
更新于2025-09-23 15:23:52
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An adapted method for analyzing 4H silicon carbide metal-oxide-semiconductor field-effect transistors
摘要： Silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) are key devices for next-generation power electronics. However, accurate determination of device parameters from 3-terminal characteristics is hampered by the presence of interface traps. Here we present a method that, in contrast to previous evaluation schemes, explicitly considers those defects. A well-tractable parametrization of the SiC/SiO2-specific interface trap spectrum is introduced that reflects the body of known data. With this ingredient, we develop an analysis that targets for an accurate determination of device parameters from simple 3-terminal characteristics. For its validation, we investigate MOSFETs with significantly different defect densities. The resulting parameters – charge carrier density, mobility and threshold voltage – are in excellent agreement with Hall effect investigations on the very same devices, avoiding systematic errors inherent to conventional evaluation techniques. With this adapted scheme, 4H-SiC power MOSFETs, even packaged, can be meaningfully characterized, speeding up innovation cycles in energy-saving power electronics.
关键词： mobility,Silicon carbide,Hall effect,interface traps,threshold voltage,MOSFET
更新于2025-09-23 15:23:52
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AlGaN/GaN MIS-HEMT with PECVD SiNx, SiON, SiO2 as Gate Dielectric and Passivation Layer
摘要： Three different insulator layers SiNx, SiON, and SiO2 were used as a gate dielectric and passivation layer in AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMT). The SiNx, SiON, and SiO2 were deposited by a plasma-enhanced chemical vapor deposition (PECVD) system. Great differences in the gate leakage current, breakdown voltage, interface traps, and current collapse were observed. The SiON MIS-HEMT exhibited the highest breakdown voltage and Ion/Ioff ratio. The SiNx MIS-HEMT performed well in current collapse but exhibited the highest gate leakage current density. The SiO2 MIS-HEMT possessed the lowest gate leakage current density but suffered from the early breakdown of the metal–insulator–semiconductor (MIS) diode. As for interface traps, the SiNx MIS-HEMT has the largest shallow trap density and the lowest deep trap density. The SiO2 MIS-HEMT has the largest deep trap density. The factors causing current collapse were confirmed by Photoluminescence (PL) spectra. Based on the direct current (DC) characteristics, SiNx and SiON both have advantages and disadvantages.
关键词： interface traps,MISHEMT,gallium nitride,PECVD,current collapse,dielectric layer
更新于2025-09-23 15:22:29
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Validation of the model of TSL isothermal decay in dosimetric α-Al2O3 crystals
摘要： New features of isothermal build-up of thermally stimulated luminescence (TSL) related to deep traps in anion-deficient alumina single crystals are revealed. It was found that the TSL build-up at 630-750 K depends on the structure of the glow curve and is associated with the presence of a high-temperature component with Tm=700 K. Isothermal TSL build-up for the peak at 573 K is well expressed in UV-irradiated samples and is very weak after sample irradiation by a pulsed electron beam. The TSL build-up for this peak is registered for the luminescence of F centres but is absent for the emission of F2+ centres and chromium ions. The obtained results confirm the validity of the kinetic model of the TSL build-up that takes into account the process of thermal ionization of the excited states of F centres in aluminum oxide.
关键词： TSL build-up,Deep traps,Thermal Ionization of F centres,Aluminum oxide,Thermally stimulated luminescence
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Conference on Electron Devices and Solid State Circuits (EDSSC) - Shenzhen, China (2018.6.6-2018.6.8)] 2018 IEEE International Conference on Electron Devices and Solid State Circuits (EDSSC) - Characterization of Transient Threshold Voltage Shifts in Enhancement- and Depletion-mode AlGaN/GaN Metal-Insulator-Semiconductor (MIS)-HEMTs
摘要： Both enhancement- and depletion-mode AlGaN/GaN metal-insulator-semiconductor HEMTs were fabricated with Al2O3 as the gate dielectric formed by atomic layer deposition (ALD). With the common problems of threshold voltage hysteresis in AlGaN/GaN MIS-HEMTs, DC I-V and fast transient frequency-dependent C-V measurements were performed to characterize the threshold voltage shifts ?Vth and hence to systematically study the underlying mechanism. The experimental results reveal that ?Vth can be as high as 1.0 V at VG,max = 5 V in transient I-V measurements despite the much lower values of 0.42 V in static and CV measurements. This has significant implications in using AlGaN/GaN MIS-HEMTs for high voltage switching applications. Besides, multi-frequency C-V measurements show that the primary ?Vth is frequency independent but the second onset of voltage shifts (?V2) shows obvious frequency dependence. These results imply the likely mechanism of slow (deep) Al2O3 interface traps accounting for ?V1 hysteresis, and fast (shallow) interface traps accounting for ?V2.
关键词： AlGaN/GaN MIS-HEMT,Al2O3/III-N interface traps (fast and slow) and threshold voltage hysteresis.
更新于2025-09-23 15:21:21
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[IEEE 2019 IEEE Asia-Pacific Microwave Conference (APMC) - Singapore, Singapore (2019.12.10-2019.12.13)] 2019 IEEE Asia-Pacific Microwave Conference (APMC) - Analytical Drain-current Model for RF Flexible Graphene Filed-Effect Transistors
摘要： An analytical Drain-current (I-V) model for radio frequency flexible graphene field-effect transistors (FGFET) is presented for the first time. In this model, a trap capacitance model is introduced by consideration of higher trapping density on plastic substrate in GFET. Moreover, a physical ‘hot’ hole injection effect model is proposed to describe abnormal shift of the Dirac point. Accurate results are observed between the simulated and measured data. This model can be used for flexible RF graphene circuits.
关键词： graphene,GFET,Dirac point,I-V model,traps,flexible
更新于2025-09-23 15:21:01
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<i>(Invited)</i> HfO <sub/>2</sub> /Al <sub/>2</sub> O <sub/>3</sub> Nanolaminate on Si <sub/>0.7</sub> Ge <sub/>0.3</sub> (100) Surface by Thermal Atomic Layer Deposition
摘要： To integrate Silicon-Germanium (SiGe) into future CMOS devices, it is essential to deposit very thin high-k dielectrics on SiGe surfaces with low density interfacial defects. In this study, Al2O3/HfO2 nanolaminate (HfO2 layers incorporated with Al2O3 monolayers) gate stacks were deposited by atomic layer deposition (ALD) using HfCl4 and H2O precursors. Electrical properties of the interfaces were quantified by capacitance-voltage (C–V) spectroscopy. Interfaces of nanolaminate stacks were found to have 2x smaller density of interface traps (Dit) than pure HfO2 gate stacks. Cross sectional TEM with Energy-dispersive X-ray spectroscopy (EDS) showed that an SiOx rich interlayer was formed between the nanolaminate and the Si0.7Ge0.3(001) substrate. The SiOx interlayer contains almost no Ge indicating that the HfCl4/TMA nanolaminate deposition reduced the GeOx in the interface. Furthermore, the SiGe surface was enriched in Ge from 30% to ~70% consistent with the HfCl4/TMA nanolaminate process reducing and redepositing Ge on the SiGe surface.
关键词： SiGe,atomic layer deposition,interface traps,high-k dielectrics,nanolaminate
更新于2025-09-23 15:21:01
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Simulation studies of the laser ablation ion source at the SHIPTRAP setup
摘要： A gas-filled miniature Radio-Frequency Quadrupole (mini-RFQ) was recently implemented into the SHIPTRAP laser ablation ion source to thermalize the laser-ablated ions and thus improve production efficiency as well as sample preparation. This source provides reference ions of various elements for online experiments with the SHIPTRAP mass spectrometer. In addition, it can be used to provide long-lived rare and radioactive isotopes available only in small sample sizes for high-precision mass measurements or to study systematic uncertainties. The performance of the laser ablation ion source was simulated using the COMSOL Multiphysics modeling software package. These studies indicate that a revised mechanical geometry and an optimized RF field improve the performance significantly.
关键词： Penning traps,Surface ionization ion source,Mass spectrometry,Laser ablation ion source
更新于2025-09-23 15:21:01