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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Comparison between Si/SiO{sub 2} and InP/Al{sub 2}O{sub 3} based MOSFETs

Electron transport properties of InP-based MOSFET as a new channel material with Al{sub 2}O{sub 3} as a high-k dielectric oxide layer in comparison with Si-based MOSFET are studied by the ensemble Monte Carlo simulation method in which the conduction band valleys in InP are based on three valley models with consideration of quantum effects (effective potential approach). I{sub d}–V{sub d} characteristics for Si-based MOSFET are in good agreement with theoretical and experimental results. Our results show that I{sub d} of InP-based MOSFET is about 2 times that of Si-based MOSFET. We simulated the diagrams of longitudinal and transverse electric fields, conduction band edge, average electron velocity, and average electron energy for Si-based MOSFET and compared the results with those for InP-based MOSFET. Our results, as was expected, show that the transverse electric field, the conduction band edge, the electron velocity, and the electron energy in a channel in the InP-based MOSFET are greater than those for Si-based MOSFET. But the longitudinal electric field behaves differently at different points of the channel.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Investigation of a pulsed current annealing method in reusing MOSFET dosimeters for in vivo IMRT dosimetry

Purpose: To explore the feasibility of pulsed current annealing in reusing metal oxide semiconductor field-effect transistor (MOSFET) dosimeters forin vivo intensity modulated radiation therapy (IMRT) dosimetry. Methods: Several MOSFETs were irradiated atd{sub max} using a 6 MV x-ray beam with 5 V on the gate and annealed with zero bias at room temperature. The percentage recovery of threshold voltage shift during multiple irradiation-annealing cycles was evaluated. Key dosimetry characteristics of the annealed MOSFET such as the dosimeter's sensitivity, reproducibility, dose linearity, and linearity of response within the dynamic range were investigated. The initial results of using the annealed MOSFETs for IMRT dosimetry practice were also presented. Results: More than 95% of threshold voltage shift can be recovered after 24-pulse current continuous annealing in 16 min. The mean sensitivity degradation was found to be 1.28%, ranging from 1.17% to 1.52%, during multiple annealing procedures. Other important characteristics of the annealed MOSFET remained nearly consistent before and after annealing. Our results showed there was no statistically significant difference between the annealed MOSFETs and their control samples in absolute dose measurements for IMRT QA (p = 0.99). The MOSFET measurements agreed with the ion chamber results on an average of 0.16% ± 0.64%. Conclusions: Pulsed current annealing provides a practical option for reusing MOSFETs to extend their operational lifetime. The current annealing circuit can be integrated into the reader, making the annealing procedure fully automatic.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

SU-E-T-145: Effects of Temporary Tachytherapy Inhibition Magnet On MOSFET Dose Measurements of Cardiovascular Implantable Electronic Devices (CIED) in Radiation Therapy Patients

Purpose: To determine the effects of temporary tachytherapy inhibition magnet on MOSFET dose measurements of cardiovascular implantable electronic devices (CIED) in radiation therapy patients. Methods: Infield and peripheral MOSFET dose measurements with 6MV photon beams were performed to evaluate dose to a CIED in the presence of a doughnut shaped temporary tachytherapy inhibition magnet. Infield measurements were done to quantify the effects of the magnetic field alone and shielding by the magnet. MOSFETs were placed inside a 20×20cm{sup 2} field at a depth of 3cm in the isocentre plane in the presence and absence of the magnet. Peripheral dose measurements were done to determine the impact of the magnet on dose to the CIED in a clinical setting. These measurements were performed at the centre, under the rim and half way between a 10×10cm{sup 2} field edge and the magnet with MOSFETS placed at the surface, 0.5cm and 1cm depths in the presence and absence of the magnet. Results: Infield measurements showed that effects of magnetic field on the MOSFET readings were within the 2% MOSFET dose measurement uncertainty; a 20% attenuation of dose under the magnet rim was observed. Peripheral dose measurements at the centre of the magnet show an 8% increase in surface dose and a 6% decrease in dose at 1cm depth. Dose under the magnet rim was reduced by approximately 68%, 45% and 25% for MOSFET placed at 0.0, 0.5 and 1.0cm bolus depths, respectively. Conclusions: The magnetic field has an insignificant effect on MOSFET dose measurements. Dose to the central region of CIED represented by centre of the magnet doughnut increases at the surface, and decreases at depths due to low energy scattering contributions from the magnet. Dose under the magnet rim, representing CIED edges, decreased significantly due to shielding.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Investigation on gate oxide reliability under gate bias screening for commercial SiC planar and trench MOSFETs

This paper evaluates the impact of the fast high gate-voltage screening technique on gate oxide reliability of commercial 1.2 kV 4H-SiC power metal-oxide-semiconductor field-effect transistors (MOSFETs) with planar and trench gate structures. The measurements are conducted on packaged devices with the intent that the results will be applicable to wafer-level screening. The threshold voltage (V th ) of SiC MOSFETs is measured before and after various screening treatments and recovery process. In addition, constant-voltage time-dependent dielectric breakdown (TDDB) measurements are performed on SiC MOSFETs to obtain the intrinsic lifetime of gate oxide. The objective of this study is to determine the optimal screening conditions and improve screening efficiency without degradation of gate oxide reliability, such as V th shift and reduced oxide intrinsic lifetime. Due to the differences in the gate oxidation process and structural design of SiC planar and trench MOSFETs, the two types of devices exhibit different oxide reliability in the screening process. The recommended screening conditions obtained in this paper reveal that SiC trench MOSFETs can accept higher screening voltages compared to SiC planar MOSFETs. Hence, it can be concluded that more efficient screening techniques can be adopted for SiC MOSFETs with thicker gate oxide to meet the requirements of industrial applications.

36 MATERIALS SCIENCE↗
DOE OSTI2014

SU-E-T-494: A MOSFET-Based In-Vivo Dosimetry System for MR Image-Guided Radiation Therapy (MR-IGRT)

Purpose: To determine if a MOSFET based in-vivo dosimetry system can be used for patients undergoing MR-IGRT. Methods: Standard and high sensitivity MOSFET detectors were used for in-field and out-of-field measurements respectively. The systems were benchmarked and calibrated against a calibrated ionization chamber on a standard 6 MV linear accelerator, and then on the MR-IGRT system. Known doses were delivered to a water phantom with the MOSFETs placed between the top of the phantom and underneath a layer of bolus and water equivalent plastic, using a 6 MV beam and a {sup 6} {sup 0}Co MR-IGRT beam. The latter was performed with and without real-time MRI-guidance during the beam delivery (MRIGRT). Results: The in-field dosimeter response was linear from 50-500 cGy with little evidence of energy dependence or change in response due to the permanent static magnetic field of the MR-IGRT system. The detector response varied by < 2% between 6 MV and {sup 6} {sup 0}Co without image guided delivery. The out-of-field dosimeter response was linear from 1-50 cGy; however the detectors did display dose rate and energy dependence as the response varied by > 20% depending on distance from isocenter used during calibration. Therefore, to use the dosimeters for out-of-field measurements they must be calibrated out-of-field. Regardless of the detector orientation in the coronal plan, the response of the MOSFETs during MRI-guided delivery increased by 5% due to induced currents from the dynamic magnetic field present with image guidance. During the MRI-guided delivery, some loss in image quality was seen when the MOSFETs were present in the imaging plane. This was mitigated by using a handheld reader without a transmitting wireless receiver. Conclusion: A MOSFET-based in-vivo dosimetry system can be used for patients receiving MR-IGRT; however the change in detector response due to the dynamic magnetic field requires a special calibration.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2015

SU-E-T-749: Thorough Calibration of MOSFET Dosimeters

Purpose: To improve the accuracy of the MOSFET calibration procedure by performing the measurement several times and calculating the average value of the calibration factor for various photon and electron energies. Methods: The output of three photon and six electron beams of Varian Trilogy linear accelerator SN 5878 was calibrated. Five reinforced standard sensitivity MOSFET dosimeters were placed in the calibration jig and connected to the Reader Module. As the backscatter material was used 7 cm of Virtual Water. The MOSFET dosimeters were covered with 1.5 cm thick bolus for the regular and SRS 6 MV beams, 3 cm bolus for 15 MV beam, 1.5 cm bolus for 6 MeV electron beam, and 2 cm bolus for the electron energies of 9, 12, 15, 18, and 22 MeV. The dosimeters were exposed to 100 MU, and the calibration factor was determined using the mobileMOSFET software. To improve the accuracy of calibration, this procedure was repeated ten times and the calibration factors were averaged. Results: As the number of calibrations was increasing the variability of calibration factors of different dosimeters was decreasing. After ten calibrations, the calibration factors for all five dosimeters were within 1% of one another for all energies, except 6 MV SRS photons and 6 MeV electrons, for which the variability was 2%. Conclusions: The described process results in calibration factors which are almost independent of modality or energy. Once calibrated, the dosimeters may be used for in-vivo dosimetry or for daily verification of the beam output. Measurement of the radiation dose under bolus and scatter to the eye are examples of frequent use of calibrated MOSFET dosimeters. The calibration factor determined for full build-up is used under these circumstances. To the best of our knowledge, such thorough procedure for calibrating MOSFET dosimeters has not been reported previously. Best Medical Canada provided MOSFET dosimeters for this project.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

TH-AB-BRA-06: MOSFET-Based Dosimetry in An MR Image-Guided Radiation Therapy System: Comparison with and Without a Static 0.3T Magnetic Field

Purpose: To compare depth-dose and surface-dose measurements without and with the magnetic field in a 0.3T MR image-guided Co-60 treatment unit using MOSFET dosimeters. Methods: MOSFET dosimeters (Best Medical Canada, model TN-502RDH-10) were placed in a solid water phantom at 5cm depth with 8cm backscatter (with the MOSFET wires in different orientations to the couch long axis) and also on the surface of an 8cm solid water phantom. The phantoms were placed in an MR image-guided Co-60 treatment machine at an SAD of 105cm to the MOSFETs. Dose measurements were performed between 50 and 200cGy at 5cm depth in a 10.5cm × 10.5cm radiation field without the magnetic field (during a machine maintenance period) and with the nominal magnetic field of 0.3T. The dose linearity was measured at 5cm depth with an orthogonal field and the angular dose dependence was measured on the surface with an orthogonal field and oblique fields at +60 degrees and −60 degrees. Results: The measured MOSFET readings at 5cm depth were linear with dose with slopes of (2.97 +/− 0.01) mV/cGy and (3.01 +/− 0.02) mV/cGy without and with the magnetic field, respectively. No statistically significant difference was found. The surface dose measurements, however, were lower by 6.4% for the AP field (2.3 σ) with magnetic field, 4.9% for the −60 degree field (1.4 σ), and 0.4% different for the +60 degree field (0.2 σ). Conclusion: There is no statistically significant difference in the dose at depth without and with the magnetic field and different orientations of the MOSFET wires. There is a statistically significant difference for the surface dose due to the influence of the magnetic field on secondary electrons from head-scatter and the build-up region in certain field orientations. Clinical surface-dose dosimetry in a magnetic field should apply asymmetric angle-dependent corrections.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

Study of Carrier Mobilities in 4H-SiC MOSFETS Using Hall Analysis

The channel conduction in 4H-SiC metal–oxide–semiconductor field effect transistors (MOSFETs) are highly impacted by charge trapping and scattering at the interface. Even though nitridation reduces the interface trap density, scattering still plays a crucial role in increasing the channel resistance in these transistors. In this work, the dominant scattering mechanisms are distinguished for inversion layer electrons and holes using temperature and body-bias-dependent Hall measurements on nitrided lateral 4H-SiC MOSFETs. The effect of the transverse electric field (E eƒƒ ) on carrier mobility is analyzed under strong inversion condition where surface roughness scattering becomes prevalent. Power law dependencies of the electron and hole Hall mobility for surface roughness scattering are determined to be E$^{-1.8}_{eƒƒ}$ and E$^{-2.4}_{eƒƒ}$, respectively, analogous to those of silicon MOSFETs. Moreover, for n-channel MOSFETs, the effect of phonon scattering is observed at zero body bias, whereas in p-channel MOSFETs, it is observed only under negative body biases. Along with the identification of regimes governed by different scattering mechanisms, these results highlight the importance of the selection of substrate doping and of E eƒƒ in controlling the value of channel mobility in 4H-SiC MOSFETs.

36 MATERIALS SCIENCE↗
NASA NTRS2009

Lightning Pin Injection Testing on MOSFETS

Lightning transients were pin-injected into metal-oxide-semiconductor field-effect transistors (MOSFETs) to induce fault modes. This report documents the test process and results, and provides a basis for subsequent lightning tests. MOSFETs may be present in DC-DC power supplies and electromechanical actuator circuits that may be used on board aircraft. Results show that unprotected MOSFET Gates are susceptible to failure, even when installed in systems in well-shielded and partial-shielded locations. MOSFET Drains and Sources are significantly less susceptible. Device impedance decreased (current increased) after every failure. Such a failure mode may lead to cascading failures, as the damaged MOSFET may allow excessive current to flow through other circuitry. Preliminary assessments on a MOSFET subjected to 20-stroke pin-injection testing demonstrate that Breakdown Voltage, Leakage Current and Threshold Voltage characteristics show damage, while the device continues to meet manufacturer performance specifications. The purpose of this research is to develop validated tools, technologies, and techniques for automated detection, diagnosis and prognosis that enable mitigation of adverse events during flight, such as from lightning transients; and to understand the interplay between lightning-induced surges and aging (i.e. humidity, vibration thermal stress, etc.) on component degradation.

Ely, Jay J.↗
DOE OSTI2015

Surface roughness scattering of electrons in bulk mosfets

Surface-roughness scattering of electrons at the Si-SiO 2 interface is a very important consideration when analyzing Si metal-oxide-semiconductor field-effect transistors (MOSFETs). Scattering reduces the mobility of the electrons and degrades the device performance. 250-nm and 50-nm bulk MOSFETs were simulated with varying device parameters and mesh sizes in order to compare the effects of surface-roughness scattering in multiple devices. The simulation framework includes the ensemble Monte Carlo method used to solve the Boltzmann transport equation coupled with a successive over-relaxation method used to solve the two-dimensional Poisson's equation. Four methods for simulating the surface-roughness scattering of electrons were implemented on both devices and compared: the constant specularity parameter, the momentum-dependent specularity parameter, and the real-space-roughness method with both uniform and varying electric fields. The specularity parameter is the probability of an electron scattering speculariy from a rough surface. It can be chosen as a constant, characterizing partially diffuse scattering of all electrons from the surface the same way, or it can be momentum dependent, where the size of rms roughness and the normal component of the electron wave number determine the probability of electron-momentum randomization. The real-space rough surface method uses the rms roughness height and correlation length of an actual MOSFET to simulate a rough interface. Due to their charge, electrons scatter from the electric field and not directly from the surface. If the electric field is kept uniform, the electrons do not perceive the roughness and scatter as if from a at surface. However, if the field is allowed to vary, the electrons scatter from the varying electric field as they would in a MOSFET. These methods were implemented for both the 50-nm and 250-nm MOSFETs, and using the rms roughness heights and correlation lengths for real devices. The current-voltage and mobility-electric field curves were plotted for each method on the two devices and compared. The conclusion is that the specularity-parameter methods are valuable as simple models for relatively smooth interfaces. However, they have limitations, as they cannot accurately describe the drastic reduction in the current and the electron mobility that occur in MOSFETs with very rough Si-SiO 2 interfaces.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Monte Carlo investigation of I-125 interseed attenuation for standard and thinner seeds in prostate brachytherapy with phantom validation using a MOSFET

Purpose: In permanent seed implant prostate brachytherapy the actual dose delivered to the patient may be less than that calculated by TG-43U1 due to interseed attenuation (ISA) and differences between prostate tissue composition and water. In this study the magnitude of the ISA effect is assessed in a phantom and in clinical prostate postimplant cases. Results are compared for seed models 6711 and 9011 with 0.8 and 0.5 mm diameters, respectively. Methods: A polymethyl methacrylate (PMMA) phantom was designed to perform ISA measurements in a simple eight-seed arrangement and at the center of an implant of 36 seeds. Monte Carlo (MC) simulation and experimental measurements using a MOSFET dosimeter were used to measure dose rate and the ISA effect. MC simulations of 15 CT-based postimplant prostate treatment plans were performed to compare the clinical impact of ISA on dose to prostate, urethra, rectum, and the volume enclosed by the 100% isodose, for 6711 and 9011 seed models. Results: In the phantom, ISA reduced the dose rate at the MOSFET position by 8.6%-18.3% (6711) and 7.8%-16.7% (9011) depending on the measurement configuration. MOSFET measured dose rates agreed with MC simulation predictions within the MOSFET measurement uncertainty, which ranged from 5.5% to 7.2% depending on the measurement configuration (k= 1, for the mean of four measurements). For 15 clinical implants, the mean ISA effect for 6711 was to reduce prostate D90 by 4.2 Gy (3%), prostate V100 by 0.5 cc (1.4%), urethra D10 by 11.3 Gy (4.4%), rectal D2cc by 5.5 Gy (4.6%), and the 100% isodose volume by 2.3 cc. For the 9011 seed the mean ISA effect reduced prostate D90 by 2.2 Gy (1.6%), prostate V100 by 0.3 cc (0.7%), urethra D10 by 8.0 Gy (3.2%), rectal D2cc by 3.1 Gy (2.7%), and the 100% isodose volume by 1.2 cc. Differences between the MC simulation and TG-43U1 consensus data for the 6711 seed model had a similar impact, reducing mean prostate D90 by 6 Gy (4.2%) and V100 by 0.6 cc (1.8%). Conclusions: ISA causes the delivered dose in prostate seed implant brachytherapy to be lower than the dose calculated by TG-43U1. MC simulation of phantom seed arrangements show that dose at a point can be reduced by up to 18% and this has been validated using a MOSFET dosimeter. Clinical simulations show that ISA reduces DVH parameter values, but the reduction is less for thinner seeds.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Characterization and Comparison of Planar and Trench Silicon Carbide (SiC) Power MOSFETs

This paper presents a comprehensive evaluation and experimental comparison of silicon carbide power MOSFETs through double pulse test. First, a universal hardware platform is designed and developed to test power semiconductor devices with various device packages and measuring requirements. Using the developed platform, the static characteristics and switching performance of the two types of SiC MOSFETs (one planar and one trench type) are evaluated under different case temperatures from 25 oC to 175 oC. Based on the evaluation data, a comparison of both SiC MOSFETs is conducted in terms of their on-state resistance, switching loss, and temperature dependent behavior. It is found that the latest trench SiC MOSFETs present similar switching loss while much lower conduction loss compared to existing commercial planar SiC MOSFETs. Moreover, the trench devices show a nearly temperature independent switching loss, which is beneficial to suppress the potential thermal runaway issue under high temperature continuous operation.

double pulse test↗
NASA NTRS1985

JMOSFET: A MOSFET parameter extractor with geometry-dependent terms

The parameters from metal-oxide-silicon field-effect transistors (MOSFETs) that are included on the Combined Release and Radiation Effects Satellite (CRRES) test chips need to be extracted to have a simple but comprehensive method that can be used in wafer acceptance, and to have a method that is sufficiently accurate that it can be used in integrated circuits. A set of MOSFET parameter extraction procedures that are directly linked to the MOSFET model equations and that facilitate the use of simple, direct curve-fitting techniques are developed. In addition, the major physical effects that affect MOSFET operation in the linear and saturation regions of operation for devices fabricated in 1.2 to 3.0 mm CMOS technology are included. The fitting procedures were designed to establish single values for such parameters as threshold voltage and transconductance and to provide for slope matching between the linear and saturation regions of the MOSFET output current-voltage curves. Four different sizes of transistors that cover a rectangular-shaped region of the channel length-width plane are analyzed.

Buehler, M. G.↗
DOE OSTI2015

Development FD-SOI MOSFET Amplifiers for Integrated Read-Out Circuit of Superconducting-Tunnel-Junction Single-Photon-Detectors

We proposed a new high-resolution single-photon infrared spectrometer for search for radiative decay of cosmic neutrino background (CνB). The superconducting-tunnel-junctions(STJs) are used as a single-photon counting device. Each STJ consists of Nb/Al/Al x O y /Al/Nb layers, and their thicknesses are optimized for the operation temperature at 370 mK cooled by a 3 He sorption refrigerator. Our STJs achieved the leak current 250 pA, and the measured data implies that a smaller area STJ fulfills our requirement. FD-SOI MOSFETs are employed to amplify the STJ signal current in order to increase signal-to-noise ratio (S/N). FD-SOI MOSFETs can be operated at cryogenic temperature of 370 mK, which reduces the noise of the signal amplification system. FD-SOI MOSFET characteristics are measured at cryogenic temperature. The Id-Vgs curve shows a sharper turn on with a higher threshold voltage and the Id-Vds curve shows a nonlinear shape in linear region at cryogenic temperature. Taking into account these effects, FD-SOI MOSFETs are available for read-out circuit of STJ detectors. The bias voltage for STJ detectors is 0.4 mV, and it must be well stabilized to deliver high performance. We proposed an FD-SOI MOSFET-based charge integrated amplifier design as a read-out circuit of STJ detectors. The requirements for an operational amplifier used in the amplifier is estimated using SPICE simulation. The op-amp is required to have a fast response (GBW ≥ 100 MHz), and it must have low power dissipation as compared to the cooling power of refrigerator.

47 OTHER INSTRUMENTATION↗
DOE OSTI2015

Application of the self-consistent quantum method for simulating the size quantization effect in the channel of a nano-scale dual gate MOSFET

Self-Consistent Quantum Method using Schrodinger-Poisson equations have been used for determining the Channel electron density of Nano-Scale MOSFETs for 6nm and 9nm thick channels. The 6nm thick MOSFET show the peak of the electron density at the middle where as the 9nm thick MOSFET shows the accumulation of the electrons at the oxide/semiconductor interface. The electron density in the channel is obtained from the diagonal elements of the density matrix; [ρ]=[1/(1+exp(β(H − μ)))] A Tridiagonal Hamiltonian Matrix [H] is constructed for the oxide/channel/oxide 1D structure for the dual gate MOSFET. This structure is discretized and Finite-Difference method is used for constructing the matrix equation. The comparison of these results which are obtained by Quantum methods are done with Semi-Classical methods.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Temperature-Dependent Short-Circuit Capability of Silicon Carbide Power MOSFETs

Our paper presents a comprehensive short-circuit ruggedness evaluation and numerical investigation of up-to-date commercial silicon carbide (SiC) MOSFETs. The short-circuit capability of three types of commercial 1200-V SiC MOSFETs is tested under various conditions, with case temperatures from 25 to 200 degrees C and dc bus voltages from 400 to 750 V. It is found that the commercial SiC MOSFETs can withstand short-circuit current for only several microseconds with a dc bus voltage of 750 V and case temperature of 200 degrees C. Moreover, the experimental short-circuit behaviors are compared, and analyzed through numerical thermal dynamic simulation. Specifically, an electrothermal model is built to estimate the device internal temperature distribution, considering the temperature-dependent thermal properties of SiC material. Based on the temperature information, a leakage current model is derived to calculate the main leakage current components (i.e., thermal, diffusion, and avalanche generation currents). Finally, numerical results show that the short-circuit failure mechanisms of SiC MOSFETs can be thermal generation current induced thermal runaway or high-temperature-related gate oxide damage.

4H↗
DOE OSTI2017

Temperature-Dependent Characterization, Modeling, and Switching Speed-Limitation Analysis of Third-Generation 10-kV SiC MOSFET

The temperature-dependent characteristics of the third-generation 10-kV/20-A SiC MOSFET including the static characteristics and switching performance are carried out in this paper. The steady-state characteristics, including saturation current, output characteristics, antiparallel diode, and parasitic capacitance, are tested. Here, a double pulse test platform is constructed including a circuit breaker and gate drive with >10-kV insulation and also a hotplate under the device under test for temperature-dependent characterization during switching transients. The switching performance is tested under various load currents and gate resistances at a 7-kV dc-link voltage from 25 to 125 C and compared with previous 10-kV MOSFETs. A simple behavioral model with its parameter extraction method is proposed to predict the temperature-dependent characteristics of the 10-kV SiC MOSFET. The switching speed limitations, including the reverse recovery of SiC MOSFET's body diode, overvoltage caused by stray inductance, crosstalk, heat sink, and electromagnetic interference to the control are discussed based on simulations and experimental results.

10-kV silicon carbide (SiC) metal–oxide–semiconduc↗
DOE OSTI2016

SU-G-IeP3-02: Characteristics of In-Vivo MOSFET Dosimeters for Diagnostic X-Ray Low-Dose Measurements

Purpose: To correct in-vivo metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters dependence on X-ray energy, dose and dose rate, and temperature in order to measure doses or exposures on several anatomic points of interest undergoing some routine radiographs. Methods: A mobile MOSFET system (BEST Medical) was carefully calibrated with X-ray at kVp of 70, 80, 100, 120, and 138 kVp, phantom temperatures at 0, 21, and 43 oC, and exposure range from 0.01 to 10 R confirmed with Raysafe and RadCal dosimeters. The MOSFETS were placed on the midline bladder or uterus, left pelvic iliac artery, left abdominal above iliac crest, abdominal midline anterior at inferior margin of stomach, and left pectoral of a large and a small body-size cadavers undergoing AP/PA chest and lumber spine radiographs using manual and automatic exposure control (AEC) with and without lead shielding. MOSTFETs and TLD chips were also placed on the stomach, sigmoid, pubic symphysis, left and right pelvic walls of another cadaver for AP pelvic manual or AEC radiography prior to and after a left hip metal implant. Results: Individual MOSFET detectors had various low-dose limits in ranged from 0.03 to 0.08 R, nonlinear response to X-ray energy, and significant temperature effect of 15%. By accumulating 10 manual exposures and 20 AEC exposures, we achieved dose measured accuracy of 6%. There were up to 8 fold increases for AEC exposure of spine and chest X-ray procedure from no shielding to with shielding. For pelvic radiography, exposure to public symphysis was the highest even higher than that of the skin. After hip implant, AEC pelvic radiograph increase exposure by 30 to 200% consistent with results of TLDs. Conclusion: Dependence of energy, temperature and dose limit were accurately corrected. We have found significant exposure for those clinical pr°ocedures and the study provided evidences for developing new clinical procedures.

60 APPLIED LIFE SCIENCES↗