259 research outputs found
Diamond-based thermo-tunnel devices for hostile environments
PhD ThesisEPSRC
BAE System
On the robustness of ultra-high voltage 4H-SiC IGBTs with an optimized retrograde p-well
The robustness of ultra-high voltage (>10kV) SiC IGBTs comprising of an optimized retrograde p-well is investigated. Under extensive TCAD simulations, we show that in addition to offering a robust control on threshold voltage and eliminating punch-through, the retrograde is highly effective in terms of reducing the stress on the gate oxide of ultra-high voltage SiC IGBTs. We show that a 10 kV SiC IGBT comprising of the retrograde p-well exhibits a much-reduced peak electric field in the gate oxide when compared with the counterpart comprising of a conventional p-well. Using an optimized retrograde p-well with depth as shallow as 1 μm, the peak electric field in the gate oxide of a 10kV rated SiC IGBT can be reduced to below 2 MV.cm -1 , a prerequisite to achieve a high-degree of reliability in high-voltage power devices. We therefore propose that the retrograde p-well is highly promising for the development of>10kV SiC IGBTs
Operation of Ultra-High Voltage (>10kV) SiC IGBTs at Elevated Temperatures:Benefits & Constraints
State of the art TCAD simulation models are used to simulate the performance of ultra-high voltage (10-20 kV) SiC IGBTs in the temperature range 300-775 K. We show that unlike Si-based counterparts, ultra-high voltage SiC IGBTs stand to gain from the temperature rise if the limit is not exceeded. We show that whilst an operation at 375 K is highly promising to achieve the most optimum on-state characteristics from SiC IGBTs, no significant degradation in the on-state current and breakdown voltage alongside with negligible rise in leakage current is observed until 550 K. Therefore, ≥10 kV SiC IGBTs are highly promising for Smart Grid and HVDC
Bioprocessing of brewers\u27 spent grain for production of xylanopectinolytic enzymes by Mucor sp.
The potential of microwave and ultrasound was evaluated for the pretreatment of brewer\u27s spent grain (BSG). Under optimal conditions of microwave and ultrasound pretreatments, reducing sugar yields per 1 g of pretreated BSG were 64.4 ± 7 mg and 39.9 ± 6 mg, respectively. Subsequently, the pretreated BSG was evaluated as a substrate for production of Xylanopectinolytic enzymes using fungi isolated from spoiled fruits. Out of twenty-nine (29) isolates recovered, Mucor sp. (AB1) isolated from Bramley apple (Malus domestica) produced xylanopectinolytic enzymes with higher specific activity, and was selected for further studies. The highest enzyme activity (137 U/g, and 67 U/g BSG, for pectinase and xylanase, respectively) was achieved in a medium that contained 15 g of BSG, at pH 6, temperature of 30 °C, supplemented with 1% xylan or pectin for inducing the production of xylanase or pectinase, respectively. The partially purified xylanopectinolytic enzymes were optimally active at 60 °C and pH 5
Retrograde p-well for 10kV-class SiC IGBTs
In this paper, we propose the use of a retrograde doping profile for the p-well for ultrahigh voltage (>10 kV) SiC IGBTs. We show that the retrograde p-well effectively addresses the punchthrough issue, whereas offering a robust control over the gate threshold voltage. Both the punchthrough elimination and the gate threshold voltage control are crucial to high-voltage vertical IGBT architectures and are determined by the limits on the doping concentration and the depth that a conventional p-well implant can have. Without any punchthrough, a 10-kV SiC IGBT consisting of retrograde p-well yields gate threshold voltages in the range of 6-7 V with a gate oxide thickness of 100 nm. Gate oxide thickness is typically restricted to 50-60 nm in SiC IGBTs if a conventional p-well with 1×10 17 cm -3 is utilized. We further show that the optimized retrograde p-well offers the most optimum switching performance. We propose that such an effective retrograde p-well, which requires low-energy shallow implants and thus key to minimize processing challenges and device development cost, is highly promising for the ultrahigh-voltage (>10 kV) SiC IGBT technology
Recent observations of peculiar Gamma-ray bursts using 3.6 m Devasthal Optical Telescope (DOT)
India has been actively involved in the follow-up observations of optical
afterglows of gamma-ray bursts (GRBs) for more than two decades, using the
country's meter-class facilities such as the 1.04 m Sampurnanand Telescope, 1.3
m Devasthal Fast Optical Telescope, 2.01 m Himalayan Chandra Telescope along
with many others in the country, utilizing the longitudinal advantage of the
place. However, since 2016, Indian astronomers have embarked on a new era of
exploration by utilizing the country's largest optical telescope, the 3.6 m
Devasthal Optical Telescope (DOT) at the Devasthal Observatory of ARIES
Nainital. This unique telescope has opened up exciting opportunities for
transient study. Starting from the installation itself, the DOT has been
actively performing the target of opportunity (ToO) observations, leading to
many interesting discoveries. Notable achievements include the contributions
towards the discovery of long GRB 211211A arising from a binary merger, the
discovery of the most delayed optical flare from GRB 210204A along with the
very faint optical afterglow (fainter than 25 mag in g-band) of GRB 200412B. We
also successfully observed the optical counterpart of the very-high-energy
(VHE) detected burst GRB 201015A using DOT. Additionally, DOT has been used for
follow-up observations of dark and orphan afterglows, along with the
observations of host galaxies associated with peculiar GRBs. More recently,
DOT's near-IR follow-up capabilities helped us to detect the first near-IR
counterpart (GRB 230409B) using an Indian telescope. In this work, we summarise
the recent discoveries and observations of GRBs using the 3.6 m DOT,
highlighting the significant contributions in revealing the mysteries of these
cosmic transients.Comment: 16 pages, 2 figures, 1 table, accepted for publication in the
Bulletin of Li\`ege Royal Society of Sciences as a part of 3
Belgo-Indian Network for Astronomy and Astrophysics (BINA) workshop, 22-24
March 202
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