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Krishna C Mandal - One of the best experts on this subject based on the ideXlab platform.
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improved n type 4h sic epitaxial radiation detectors by edge termination
IEEE Transactions on Nuclear Science, 2015Co-Authors: Khai V Nguyen, Mohammad A Mannan, Krishna C MandalAbstract:A new edge termination with ${\rm SiO}_{2}$ and ${\rm Si}_{3}{{\rm N}_4}$ passivating layers has been developed and is shown to be a very effective method for improving energy resolution of $20 ~\mu \hbox{m}$ n-type 4H-SiC epilayer Schottky barrier radiation detectors. The junction properties of the fabricated detectors before and after edge termination were studied by current-voltage (I-V) and capacitance-voltage (C-V) measurements. A thermionic emission model applied to the forward I-V characteristics showed surface barrier height of $\sim 1.4 ~\hbox{eV}$ and diode ideality factor of $\sim 1.1$ . The C-V measurements showed a doping concentration of $1.8 \times {10^{14}} ~\hbox{cm}^{ - 3}$ which ensured a fully depleted ${(\sim 20 ~\mu \hbox{m})}$ detector at bias voltages as low as $\sim 70 ~\hbox{V}$ . Alpha Spectroscopy measurements revealed an improved energy resolution from $\sim 0.7 \% $ to $\sim 0.4\% $ for 5.48 MeV Alpha particles. Deep level transient Spectroscopy (DLTS) measurements have shown a decreased concentration of ${{\rm Z}_{1/2}}$ defect levels in detectors following edge termination.
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high barrier schottky contact on n type 4h sic epitaxial layer and studies of defect levels by deep level transient Spectroscopy dlts
Proceedings of SPIE, 2015Co-Authors: Khai V Nguyen, Rahmi O Pak, Cihan Oner, Mohammad A Mannan, Krishna C MandalAbstract:High barrier Schottky contact has been fabricated on 50 μm n-type 4H-SiC epitaxial layers grown on 350 μm thick substrate 8° off-cut towards the [1120] direction. The 4H-SiC epitaxial wafer was diced into 10 x 10 mm 2 samples. The metal-semiconductor junctions were fabricated by photolithography and dc sputtering with ruthenium (Ru). The junction properties were characterized through current-voltage (I-V) and capacitance-voltage (C-V) measurements. Detectors were characterized by Alpha Spectroscopy measurements in terms of energy resolution and charge collection efficiency using a 0.1 μCi 241 Am radiation source. It was found that detectors fabricated from high work function rare transition metal Ru demonstrated very low leakage current and significant improvement of detector performance. Defect characterization of the epitaxial layers was conducted by deep level transient Spectroscopy (DLTS) to thoroughly investigate the defect levels in the active region. The presence of a new defect level induced by this rare transition metal-semiconductor interface has been identified and characterized.
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effect of z 1 2 eh 5 and ci1 deep defects on the performance of n type 4h sic epitaxial layers schottky detectors Alpha Spectroscopy and deep level transient Spectroscopy studies
Journal of Applied Physics, 2014Co-Authors: Mohammad A Mannan, Sandeep K Chaudhuri, Khai V Nguyen, Krishna C MandalAbstract:Spectroscopic performance of Schottky barrier Alpha particle detectors fabricated on 50 μm thick n-type 4H-SiC epitaxial layers containing Z1/2, EH5, and Ci1 deep levels were investigated. The device performance was evaluated on the basis of junction current/capacitance characterization and Alpha pulse-height Spectroscopy. Capacitance mode deep level transient Spectroscopy revealed the presence of the above-mentioned deep levels along with two shallow level defects related to titanium impurities (Ti(h) and Ti(c)) and an unidentified deep electron trap located at 2.4 eV below the conduction band minimum, which is being reported for the first time. The concentration of the lifetime killer Z1/2 defects was found to be 1.7 × 1013 cm−3. The charge transport and collection efficiency results obtained from the Alpha particle pulse-height Spectroscopy were interpreted using a drift-diffusion charge transport model. Based on these investigations, the physics behind the correlation of the detector properties viz., energy resolution and charge collection efficiency, the junction properties like uniformity in barrier-height, leakage current, and effective doping concentration, and the presence of defects has been discussed in details. The studies also revealed that the dominating contribution to the charge collection efficiency was due to the diffusion of charge carriers generated in the neutral region of the detector. The 10 mm2 large area detectors demonstrated an impressive energy resolution of 1.8% for 5486 keV Alpha particles at an optimized operating reverse bias of 130 V.
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experimental determination of electron hole pair creation energy in 4h sic epitaxial layer an absolute calibration approach
Applied Physics Letters, 2013Co-Authors: Sandeep K Chaudhuri, Kelvin J Zavalla, Krishna C MandalAbstract:Electron-hole pair creation energy (e) has been determined from Alpha Spectroscopy using 4H-SiC epitaxial layer Schottky detectors and a pulser calibration technique. We report an experimentally obtained e value of 7.28 eV in 4H-SiC. The obtained e value and theoretical models were used to calculate a Fano factor of 0.128 for 5.48 MeV Alpha particles. The contributions of different factors to the ultimate Alpha peak broadening in pulse-height spectra were determined using the calculated e value and Monte-Carlo simulations. The determined e value was verified using a drift-diffusion model of variation of charge collection efficiency with applied bias.
W W Heidbrink - One of the best experts on this subject based on the ideXlab platform.
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diagnosis of fast ions produced by negative ion neutral beam injection with fast ion deuterium Alpha Spectroscopy
Review of Scientific Instruments, 2019Co-Authors: C M Muscatello, W W Heidbrink, R L Boivin, C Chrystal, C Collins, Y Fujiwara, H YamaguchiAbstract:Negative-ion neutral-beam injection (NNBI) is an important source of heating and current drive for next-step fusion devices where the injected energy can range from hundreds of keV to 1 MeV. Few diagnostics are suitable for phase-space resolved measurements of fast ions with energy in excess of 100 keV. A study to assess the feasibility of fast-ion deuterium-Alpha (FIDA) Spectroscopy to diagnose high-energy ions produced by NNBI is presented. Case studies with the Large Helical Device (LHD) and JT-60SA illustrate possible solutions for the measurement. The distribution function of fast ions produced by NNBI is calculated for both devices, and the FIDA spectrum is predicted by synthetic diagnostic simulation. Results with 180 keV NNBI in LHD show that, with a judicious choice of viewing geometry, the FIDA intensity is comparable to that obtained with the existing FIDA system. The measurement is more challenging with the 500 keV NNBI in JT-60SA. Simulations predict the FIDA intensity to be about 1% of the background bremsstrahlung, which is small compared to existing FIDA implementations with positive neutral-beam injection where signal levels are an order of magnitude larger. The sampling time required to extract the small FIDA signal is determined using a probabilistic approach. Results indicate that long averaging periods, from ones to tens of seconds, are needed to resolve the FIDA signal in JT-60SA. These long averaging times are suitable in long-pulse (∼100 s), steady-state devices like JT-60SA where an important measurement objective is the spatial profile of the slowing-down distribution of fast ions.Negative-ion neutral-beam injection (NNBI) is an important source of heating and current drive for next-step fusion devices where the injected energy can range from hundreds of keV to 1 MeV. Few diagnostics are suitable for phase-space resolved measurements of fast ions with energy in excess of 100 keV. A study to assess the feasibility of fast-ion deuterium-Alpha (FIDA) Spectroscopy to diagnose high-energy ions produced by NNBI is presented. Case studies with the Large Helical Device (LHD) and JT-60SA illustrate possible solutions for the measurement. The distribution function of fast ions produced by NNBI is calculated for both devices, and the FIDA spectrum is predicted by synthetic diagnostic simulation. Results with 180 keV NNBI in LHD show that, with a judicious choice of viewing geometry, the FIDA intensity is comparable to that obtained with the existing FIDA system. The measurement is more challenging with the 500 keV NNBI in JT-60SA. Simulations predict the FIDA intensity to be about 1% of the b...
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diagnosis of fast ions produced by negative ion neutral beam injection with fast ion deuterium Alpha Spectroscopy
Review of Scientific Instruments, 2019Co-Authors: C M Muscatello, W W Heidbrink, R L Boivin, C Chrystal, C Collins, Y Fujiwara, H YamaguchiAbstract:Negative-ion neutral-beam injection (NNBI) is an important source of heating and current drive for next-step fusion devices where the injected energy can range from hundreds of keV to 1 MeV. Few diagnostics are suitable for phase-space resolved measurements of fast ions with energy in excess of 100 keV. A study to assess the feasibility of fast-ion deuterium-Alpha (FIDA) Spectroscopy to diagnose high-energy ions produced by NNBI is presented. Case studies with the Large Helical Device (LHD) and JT-60SA illustrate possible solutions for the measurement. The distribution function of fast ions produced by NNBI is calculated for both devices, and the FIDA spectrum is predicted by synthetic diagnostic simulation. Results with 180 keV NNBI in LHD show that, with a judicious choice of viewing geometry, the FIDA intensity is comparable to that obtained with the existing FIDA system. The measurement is more challenging with the 500 keV NNBI in JT-60SA. Simulations predict the FIDA intensity to be about 1% of the background bremsstrahlung, which is small compared to existing FIDA implementations with positive neutral-beam injection where signal levels are an order of magnitude larger. The sampling time required to extract the small FIDA signal is determined using a probabilistic approach. Results indicate that long averaging periods, from ones to tens of seconds, are needed to resolve the FIDA signal in JT-60SA. These long averaging times are suitable in long-pulse (∼100 s), steady-state devices like JT-60SA where an important measurement objective is the spatial profile of the slowing-down distribution of fast ions.
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on velocity space sensitivity of fast ion d Alpha Spectroscopy
Plasma Physics and Controlled Fusion, 2014Co-Authors: M Salewski, A S Jacobsen, B Geiger, S B Korsholm, Frank Leipold, S K Nielsen, D Moseev, W W Heidbrink, Jens Madsen, Juul J RasmussenAbstract:The velocity-space observation regions and sensitivities in fast-ion Dα (FIDA) Spectroscopy measurements are often described by so-called weight functions. Here we derive expressions for FIDA weight functions accounting for the Doppler shift, Stark splitting, and the charge-exchange reaction and electron transition probabilities. Our approach yields an efficient way to calculate correctly scaled FIDA weight functions and implies simple analytic expressions for their boundaries that separate the triangular observable regions in (v||, v⊥)-space from the unobservable regions. These boundaries are determined by the Doppler shift and Stark splitting and could until now only be found by numeric simulation.
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measurements of fast ion acceleration at cyclotron harmonics using balmer Alpha Spectroscopy
Plasma Physics and Controlled Fusion, 2007Co-Authors: W W Heidbrink, Y Luo, K H Burrell, R W Harvey, R I Pinsker, E RuskovAbstract:Combined neutral beam injection and fast wave heating at the fourth and fifth cyclotron harmonics accelerate fast ions in the DIII-D tokamak. Measurements with a nine-channel fast-ion D-Alpha (FIDA) diagnostic indicate the formation of a fast-ion tail above the injection energy. Tail formation correlates with enhancement of the d–d neutron rate above the value that is expected in the absence of fast-wave acceleration. FIDA spatial profiles and fast-ion pressure profiles inferred from the equilibrium both indicate that the acceleration is near the magnetic axis for a centrally located resonance layer. The enhancement is largest 8–10 cm beyond the radius where the wave frequency equals the cyclotron harmonic, probably due to a combination of Doppler-shift and orbital effects. The fast-ion distribution function calculated by the CQL3D Fokker– Planck code is fairly consistent with the data. (Some figures in this article are in colour only in the electronic version)
Sandeep K Chaudhuri - One of the best experts on this subject based on the ideXlab platform.
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effect of z 1 2 eh 5 and ci1 deep defects on the performance of n type 4h sic epitaxial layers schottky detectors Alpha Spectroscopy and deep level transient Spectroscopy studies
Journal of Applied Physics, 2014Co-Authors: Mohammad A Mannan, Sandeep K Chaudhuri, Khai V Nguyen, Krishna C MandalAbstract:Spectroscopic performance of Schottky barrier Alpha particle detectors fabricated on 50 μm thick n-type 4H-SiC epitaxial layers containing Z1/2, EH5, and Ci1 deep levels were investigated. The device performance was evaluated on the basis of junction current/capacitance characterization and Alpha pulse-height Spectroscopy. Capacitance mode deep level transient Spectroscopy revealed the presence of the above-mentioned deep levels along with two shallow level defects related to titanium impurities (Ti(h) and Ti(c)) and an unidentified deep electron trap located at 2.4 eV below the conduction band minimum, which is being reported for the first time. The concentration of the lifetime killer Z1/2 defects was found to be 1.7 × 1013 cm−3. The charge transport and collection efficiency results obtained from the Alpha particle pulse-height Spectroscopy were interpreted using a drift-diffusion charge transport model. Based on these investigations, the physics behind the correlation of the detector properties viz., energy resolution and charge collection efficiency, the junction properties like uniformity in barrier-height, leakage current, and effective doping concentration, and the presence of defects has been discussed in details. The studies also revealed that the dominating contribution to the charge collection efficiency was due to the diffusion of charge carriers generated in the neutral region of the detector. The 10 mm2 large area detectors demonstrated an impressive energy resolution of 1.8% for 5486 keV Alpha particles at an optimized operating reverse bias of 130 V.
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experimental determination of electron hole pair creation energy in 4h sic epitaxial layer an absolute calibration approach
Applied Physics Letters, 2013Co-Authors: Sandeep K Chaudhuri, Kelvin J Zavalla, Krishna C MandalAbstract:Electron-hole pair creation energy (e) has been determined from Alpha Spectroscopy using 4H-SiC epitaxial layer Schottky detectors and a pulser calibration technique. We report an experimentally obtained e value of 7.28 eV in 4H-SiC. The obtained e value and theoretical models were used to calculate a Fano factor of 0.128 for 5.48 MeV Alpha particles. The contributions of different factors to the ultimate Alpha peak broadening in pulse-height spectra were determined using the calculated e value and Monte-Carlo simulations. The determined e value was verified using a drift-diffusion model of variation of charge collection efficiency with applied bias.
Mohammad A Mannan - One of the best experts on this subject based on the ideXlab platform.
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improved n type 4h sic epitaxial radiation detectors by edge termination
IEEE Transactions on Nuclear Science, 2015Co-Authors: Khai V Nguyen, Mohammad A Mannan, Krishna C MandalAbstract:A new edge termination with ${\rm SiO}_{2}$ and ${\rm Si}_{3}{{\rm N}_4}$ passivating layers has been developed and is shown to be a very effective method for improving energy resolution of $20 ~\mu \hbox{m}$ n-type 4H-SiC epilayer Schottky barrier radiation detectors. The junction properties of the fabricated detectors before and after edge termination were studied by current-voltage (I-V) and capacitance-voltage (C-V) measurements. A thermionic emission model applied to the forward I-V characteristics showed surface barrier height of $\sim 1.4 ~\hbox{eV}$ and diode ideality factor of $\sim 1.1$ . The C-V measurements showed a doping concentration of $1.8 \times {10^{14}} ~\hbox{cm}^{ - 3}$ which ensured a fully depleted ${(\sim 20 ~\mu \hbox{m})}$ detector at bias voltages as low as $\sim 70 ~\hbox{V}$ . Alpha Spectroscopy measurements revealed an improved energy resolution from $\sim 0.7 \% $ to $\sim 0.4\% $ for 5.48 MeV Alpha particles. Deep level transient Spectroscopy (DLTS) measurements have shown a decreased concentration of ${{\rm Z}_{1/2}}$ defect levels in detectors following edge termination.
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high barrier schottky contact on n type 4h sic epitaxial layer and studies of defect levels by deep level transient Spectroscopy dlts
Proceedings of SPIE, 2015Co-Authors: Khai V Nguyen, Rahmi O Pak, Cihan Oner, Mohammad A Mannan, Krishna C MandalAbstract:High barrier Schottky contact has been fabricated on 50 μm n-type 4H-SiC epitaxial layers grown on 350 μm thick substrate 8° off-cut towards the [1120] direction. The 4H-SiC epitaxial wafer was diced into 10 x 10 mm 2 samples. The metal-semiconductor junctions were fabricated by photolithography and dc sputtering with ruthenium (Ru). The junction properties were characterized through current-voltage (I-V) and capacitance-voltage (C-V) measurements. Detectors were characterized by Alpha Spectroscopy measurements in terms of energy resolution and charge collection efficiency using a 0.1 μCi 241 Am radiation source. It was found that detectors fabricated from high work function rare transition metal Ru demonstrated very low leakage current and significant improvement of detector performance. Defect characterization of the epitaxial layers was conducted by deep level transient Spectroscopy (DLTS) to thoroughly investigate the defect levels in the active region. The presence of a new defect level induced by this rare transition metal-semiconductor interface has been identified and characterized.
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effect of z 1 2 eh 5 and ci1 deep defects on the performance of n type 4h sic epitaxial layers schottky detectors Alpha Spectroscopy and deep level transient Spectroscopy studies
Journal of Applied Physics, 2014Co-Authors: Mohammad A Mannan, Sandeep K Chaudhuri, Khai V Nguyen, Krishna C MandalAbstract:Spectroscopic performance of Schottky barrier Alpha particle detectors fabricated on 50 μm thick n-type 4H-SiC epitaxial layers containing Z1/2, EH5, and Ci1 deep levels were investigated. The device performance was evaluated on the basis of junction current/capacitance characterization and Alpha pulse-height Spectroscopy. Capacitance mode deep level transient Spectroscopy revealed the presence of the above-mentioned deep levels along with two shallow level defects related to titanium impurities (Ti(h) and Ti(c)) and an unidentified deep electron trap located at 2.4 eV below the conduction band minimum, which is being reported for the first time. The concentration of the lifetime killer Z1/2 defects was found to be 1.7 × 1013 cm−3. The charge transport and collection efficiency results obtained from the Alpha particle pulse-height Spectroscopy were interpreted using a drift-diffusion charge transport model. Based on these investigations, the physics behind the correlation of the detector properties viz., energy resolution and charge collection efficiency, the junction properties like uniformity in barrier-height, leakage current, and effective doping concentration, and the presence of defects has been discussed in details. The studies also revealed that the dominating contribution to the charge collection efficiency was due to the diffusion of charge carriers generated in the neutral region of the detector. The 10 mm2 large area detectors demonstrated an impressive energy resolution of 1.8% for 5486 keV Alpha particles at an optimized operating reverse bias of 130 V.
Khai V Nguyen - One of the best experts on this subject based on the ideXlab platform.
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improved n type 4h sic epitaxial radiation detectors by edge termination
IEEE Transactions on Nuclear Science, 2015Co-Authors: Khai V Nguyen, Mohammad A Mannan, Krishna C MandalAbstract:A new edge termination with ${\rm SiO}_{2}$ and ${\rm Si}_{3}{{\rm N}_4}$ passivating layers has been developed and is shown to be a very effective method for improving energy resolution of $20 ~\mu \hbox{m}$ n-type 4H-SiC epilayer Schottky barrier radiation detectors. The junction properties of the fabricated detectors before and after edge termination were studied by current-voltage (I-V) and capacitance-voltage (C-V) measurements. A thermionic emission model applied to the forward I-V characteristics showed surface barrier height of $\sim 1.4 ~\hbox{eV}$ and diode ideality factor of $\sim 1.1$ . The C-V measurements showed a doping concentration of $1.8 \times {10^{14}} ~\hbox{cm}^{ - 3}$ which ensured a fully depleted ${(\sim 20 ~\mu \hbox{m})}$ detector at bias voltages as low as $\sim 70 ~\hbox{V}$ . Alpha Spectroscopy measurements revealed an improved energy resolution from $\sim 0.7 \% $ to $\sim 0.4\% $ for 5.48 MeV Alpha particles. Deep level transient Spectroscopy (DLTS) measurements have shown a decreased concentration of ${{\rm Z}_{1/2}}$ defect levels in detectors following edge termination.
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high barrier schottky contact on n type 4h sic epitaxial layer and studies of defect levels by deep level transient Spectroscopy dlts
Proceedings of SPIE, 2015Co-Authors: Khai V Nguyen, Rahmi O Pak, Cihan Oner, Mohammad A Mannan, Krishna C MandalAbstract:High barrier Schottky contact has been fabricated on 50 μm n-type 4H-SiC epitaxial layers grown on 350 μm thick substrate 8° off-cut towards the [1120] direction. The 4H-SiC epitaxial wafer was diced into 10 x 10 mm 2 samples. The metal-semiconductor junctions were fabricated by photolithography and dc sputtering with ruthenium (Ru). The junction properties were characterized through current-voltage (I-V) and capacitance-voltage (C-V) measurements. Detectors were characterized by Alpha Spectroscopy measurements in terms of energy resolution and charge collection efficiency using a 0.1 μCi 241 Am radiation source. It was found that detectors fabricated from high work function rare transition metal Ru demonstrated very low leakage current and significant improvement of detector performance. Defect characterization of the epitaxial layers was conducted by deep level transient Spectroscopy (DLTS) to thoroughly investigate the defect levels in the active region. The presence of a new defect level induced by this rare transition metal-semiconductor interface has been identified and characterized.
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effect of z 1 2 eh 5 and ci1 deep defects on the performance of n type 4h sic epitaxial layers schottky detectors Alpha Spectroscopy and deep level transient Spectroscopy studies
Journal of Applied Physics, 2014Co-Authors: Mohammad A Mannan, Sandeep K Chaudhuri, Khai V Nguyen, Krishna C MandalAbstract:Spectroscopic performance of Schottky barrier Alpha particle detectors fabricated on 50 μm thick n-type 4H-SiC epitaxial layers containing Z1/2, EH5, and Ci1 deep levels were investigated. The device performance was evaluated on the basis of junction current/capacitance characterization and Alpha pulse-height Spectroscopy. Capacitance mode deep level transient Spectroscopy revealed the presence of the above-mentioned deep levels along with two shallow level defects related to titanium impurities (Ti(h) and Ti(c)) and an unidentified deep electron trap located at 2.4 eV below the conduction band minimum, which is being reported for the first time. The concentration of the lifetime killer Z1/2 defects was found to be 1.7 × 1013 cm−3. The charge transport and collection efficiency results obtained from the Alpha particle pulse-height Spectroscopy were interpreted using a drift-diffusion charge transport model. Based on these investigations, the physics behind the correlation of the detector properties viz., energy resolution and charge collection efficiency, the junction properties like uniformity in barrier-height, leakage current, and effective doping concentration, and the presence of defects has been discussed in details. The studies also revealed that the dominating contribution to the charge collection efficiency was due to the diffusion of charge carriers generated in the neutral region of the detector. The 10 mm2 large area detectors demonstrated an impressive energy resolution of 1.8% for 5486 keV Alpha particles at an optimized operating reverse bias of 130 V.