ABSTRACT The Army Research Laboratory has collaborated with Cree, Inc. and Silicon Power Corp. to... more ABSTRACT The Army Research Laboratory has collaborated with Cree, Inc. and Silicon Power Corp. to develop 9 kV-blocking, 1.0 cm(2) Super-GTOs. In this study, several 1.0 cm(2) GTOs were individually switched up to 6.0 kA in a low-inductance, high di/dt (2.1 KA/mu s) circuit to evaluate turn-on delay and optimize the gate control. Turn-on delay was evaluated relative to gate drive current, and the delay was reduced by 1.1 mu s when gate amplitude was increased from 1 A to 8 A. Increasing gate current delivered to each GTO also successfully reduced variation in turn-on delay from device to device by at least 50%, and mitigated mismatch in turn-on between pairs of GTOs switched in parallel. As silicon carbide material processing and device development continue to evolve, the ultimate solution will be to reduce remaining material defects and to control minority carrier diffusion length through more uniform doping across the wafer. These steps will enable modules of parallel GTOs to perform at maximum capability.
It has been demonstrated experimentally that the switch-off time of a high-voltage power (1.8 kV,... more It has been demonstrated experimentally that the switch-off time of a high-voltage power (1.8 kV, 3.8 A) 4H-SiC bipolar junction transistor in the deep-saturation mode can be decreased from 200 to 25 ns by using an appropriate switch-off base signal. In such conditions, the switch-off time in the common-emitter configuration can be shorter than the switch-on time.
ABSTRACT Alkali (Rb and Cs) and alkaline earth (Ca, Sr, and Ba) elements have been investigated a... more ABSTRACT Alkali (Rb and Cs) and alkaline earth (Ca, Sr, and Ba) elements have been investigated as interface passivation materials for metal-oxide-semiconductor field-effect transistors (MOSFETs) on 4H-SiC (0001). While the alkali elements Rb and Cs result in field-effect mobility (mu FE) values > 25 cm(2)/V.s, the alkaline earth elements Sr and Ba resulted in higher lFE values of 40 and 85 cm(2)/V.s, respectively. The Ba-modified MOSFETs show a slight decrease in mobility with heating to 150 degrees C, as expected when mobility is not interface-trap-limited, but phonon-scattering-limited. With a Ba interface layer, the interface state density 0.25 eV below the conduction band is similar to 3 x 10(11) cm(-2) eV(-1), lower than that obtained with nitric oxide passivation. Devices show stable threshold voltage under 2 MV/cm gate bias stress at 175 degrees C, indicating no mobile ions. Secondaryion mass spectrometry shows that the Sr and Ba stay predominantly at the interface after oxidation anneals. (C) 2014 AIP Publishing LLC.
4H-SiC RF bipolar junction transistors (BJTs) have been designed and tested at 425 MHz for the fi... more 4H-SiC RF bipolar junction transistors (BJTs) have been designed and tested at 425 MHz for the first time. Both epitaxial and implanted emitter structures have been fabricated. It has been established that the implanted emitter structure has very low current gain (∼1) due to the implant damage which cannot be totally removed by the high temperature activation anneal. The epitaxial
Rapid advances in technology force a quest for computer architectures that exploit new opportunit... more Rapid advances in technology force a quest for computer architectures that exploit new opportunities and shed existing mechanisms that do not scale. Current architectures, such as hardware scheduled superscalars, are already hitting performance and complexity limits and cannot be scaled indefinitely. The Reconfigurable Architecture Workstation (Raw) is a simple, wire-efficient architecture that scales with increasing VLSI gate densities and attempts to provide performance that is at least comparable to that provided by scaling an existing architecture, but that can achieve orders of magnitude more performance for applications in which the compiler can discover and statically schedule fine-grain parallelism.
Abstract: Silicon Carbide (SiC) is a promising new material for high power high temperature elect... more Abstract: Silicon Carbide (SiC) is a promising new material for high power high temperature electronics applications. SiC Schottky diodes are already finding wide acceptance in designing high efficiency power electronic systems. We present TCAD and Verilog-A ...
... 1. Introduction. Silicon carbide (SiC) thyristors demonstrate great performance advantages ov... more ... 1. Introduction. Silicon carbide (SiC) thyristors demonstrate great performance advantages over Si or GaAs devices because of the higher breakdown electric field, carrier saturation velocities, and thermal conductivity of SiC. ...
ABSTRACT The Army Research Laboratory has collaborated with Cree, Inc. and Silicon Power Corp. to... more ABSTRACT The Army Research Laboratory has collaborated with Cree, Inc. and Silicon Power Corp. to develop 9 kV-blocking, 1.0 cm(2) Super-GTOs. In this study, several 1.0 cm(2) GTOs were individually switched up to 6.0 kA in a low-inductance, high di/dt (2.1 KA/mu s) circuit to evaluate turn-on delay and optimize the gate control. Turn-on delay was evaluated relative to gate drive current, and the delay was reduced by 1.1 mu s when gate amplitude was increased from 1 A to 8 A. Increasing gate current delivered to each GTO also successfully reduced variation in turn-on delay from device to device by at least 50%, and mitigated mismatch in turn-on between pairs of GTOs switched in parallel. As silicon carbide material processing and device development continue to evolve, the ultimate solution will be to reduce remaining material defects and to control minority carrier diffusion length through more uniform doping across the wafer. These steps will enable modules of parallel GTOs to perform at maximum capability.
It has been demonstrated experimentally that the switch-off time of a high-voltage power (1.8 kV,... more It has been demonstrated experimentally that the switch-off time of a high-voltage power (1.8 kV, 3.8 A) 4H-SiC bipolar junction transistor in the deep-saturation mode can be decreased from 200 to 25 ns by using an appropriate switch-off base signal. In such conditions, the switch-off time in the common-emitter configuration can be shorter than the switch-on time.
ABSTRACT Alkali (Rb and Cs) and alkaline earth (Ca, Sr, and Ba) elements have been investigated a... more ABSTRACT Alkali (Rb and Cs) and alkaline earth (Ca, Sr, and Ba) elements have been investigated as interface passivation materials for metal-oxide-semiconductor field-effect transistors (MOSFETs) on 4H-SiC (0001). While the alkali elements Rb and Cs result in field-effect mobility (mu FE) values > 25 cm(2)/V.s, the alkaline earth elements Sr and Ba resulted in higher lFE values of 40 and 85 cm(2)/V.s, respectively. The Ba-modified MOSFETs show a slight decrease in mobility with heating to 150 degrees C, as expected when mobility is not interface-trap-limited, but phonon-scattering-limited. With a Ba interface layer, the interface state density 0.25 eV below the conduction band is similar to 3 x 10(11) cm(-2) eV(-1), lower than that obtained with nitric oxide passivation. Devices show stable threshold voltage under 2 MV/cm gate bias stress at 175 degrees C, indicating no mobile ions. Secondaryion mass spectrometry shows that the Sr and Ba stay predominantly at the interface after oxidation anneals. (C) 2014 AIP Publishing LLC.
4H-SiC RF bipolar junction transistors (BJTs) have been designed and tested at 425 MHz for the fi... more 4H-SiC RF bipolar junction transistors (BJTs) have been designed and tested at 425 MHz for the first time. Both epitaxial and implanted emitter structures have been fabricated. It has been established that the implanted emitter structure has very low current gain (∼1) due to the implant damage which cannot be totally removed by the high temperature activation anneal. The epitaxial
Rapid advances in technology force a quest for computer architectures that exploit new opportunit... more Rapid advances in technology force a quest for computer architectures that exploit new opportunities and shed existing mechanisms that do not scale. Current architectures, such as hardware scheduled superscalars, are already hitting performance and complexity limits and cannot be scaled indefinitely. The Reconfigurable Architecture Workstation (Raw) is a simple, wire-efficient architecture that scales with increasing VLSI gate densities and attempts to provide performance that is at least comparable to that provided by scaling an existing architecture, but that can achieve orders of magnitude more performance for applications in which the compiler can discover and statically schedule fine-grain parallelism.
Abstract: Silicon Carbide (SiC) is a promising new material for high power high temperature elect... more Abstract: Silicon Carbide (SiC) is a promising new material for high power high temperature electronics applications. SiC Schottky diodes are already finding wide acceptance in designing high efficiency power electronic systems. We present TCAD and Verilog-A ...
... 1. Introduction. Silicon carbide (SiC) thyristors demonstrate great performance advantages ov... more ... 1. Introduction. Silicon carbide (SiC) thyristors demonstrate great performance advantages over Si or GaAs devices because of the higher breakdown electric field, carrier saturation velocities, and thermal conductivity of SiC. ...
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Papers by Anant Agarwal