Papers by Author: Pavel A. Ivanov

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Authors: Sergey L. Rumyantsev, Michael S. Shur, Michael E. Levinshtein, Pavel A. Ivanov, John W. Palmour, Anant K. Agarwal, Sarit Dhar
Abstract: 4H-SiC MOSFETs with an epitaxial channel and NO postoxidation annealing have Si-like dependencies of noise on gate voltage. Such dependencies indicate that the density of the negatively charged oxide traps responsible for 1/f noise, Ntv, does not depend on the position of the Fermi level. The Ntv was found to be ~ 2×1019 cm-3eV-1. This value is considerably smaller than previously measured for transistors with ion implanted channels.
Authors: Pavel A. Ivanov, Alexander S. Potapov, Tat'yana P. Samsonova
Abstract: Forward current-voltage characteristics of non-ideal Ti / 4H-SiC Schottky barriers with ideality factor n = 1.1 - 1.2 have been analyzed. The non-ideality is considered as a result of formation of a thin intermediate dielectric layer between the deposited titanium layer and 4H-SiC. Using experimental current-voltage characteristics, the electro-physical characteristics of Ti contacts such as the energy barrier height, the thickness of the intermediate layer and the energy distribution of the interface trap density are determined.
Authors: Pavel A. Ivanov, Michael E. Levinshtein, Anant K. Agarwal, Sumi Krishnaswami, John W. Palmour
Abstract: For 1-kV, 30-A 4H-SiC epitaxial emitter npn bipolar junction transistors, the dependence of the common-emitter current gain β on the collector current IC were measured at elevated temperatures. The collector-emitter voltage was fixed (at 100 V voltage) to provide an active operation mode at all collector currents varying in a wide range from 150 mA to 40 A (current densities 24 - 6350 A/cm2). The maximum room temperature current gain was measured to be βmax = 40 (IC = 7 A) while βmax = 32 (IC = 10 A) at 250oC. The β-IC dependences were simulated using a model which takes into account the main processes affecting the current gain. Minority carrier lifetimes and surface recombination velocity were obtained by means of those considerations.
Authors: Pavel A. Ivanov, Michael E. Levinshtein, Anant K. Agarwal, John W. Palmour, Sei Hyung Ryu
Authors: Michael E. Levinshtein, Pavel A. Ivanov, John W. Palmour, Anant K. Agarwal, Mrinal K. Das
Abstract: We report on specific features of forward voltage degradation of 4H-SiC p-i-n diodes in the pulse mode. It is shown that pulse stresses with a pulse duration shorter than several milliseconds cause substantially smaller forward voltage drift in comparison with a dc stress with the same charge passed through the diodes and the same distribution of injected carriers. A self-recovery of the forward voltage is observed at room temperature.
Authors: Pavel A. Ivanov, Igor V. Grekhov
Abstract: High-voltage (900 V) 4H-SiC Schottky-barrier diodes (SBD) terminated with guard pnjunction were fabricated and investigated. The guard pn-junction was formed by room temperature boron implantation followed by high temperature annealing. Owing to the transient enhanced boron diffusion during anneal, the depth of guard pn-junction is about 1.7 μm, that is approximately 1 μm deeper than the expected average range of 11B ions in 4H-SiC. The maximum reverse voltage of 4H-SiC SBD produced has been found to be limited by the avalanche breakdown in cylindrical portion of planar pn-junction. The value of the breakdown voltage of 910 V is close to theoretical one calculated for the dopant density  = 2.5×1015 cm-3, n-base thickness d = 12.5 μm and junction curvature rj = 1.7 μm. Dynamic (pulse) reverse current-voltage characteristics were measured in the breakdown regime. It was found that dynamic breakdown voltage increases with shortening the pulse duration. Due to homogeneous avalanche breakdown at the edge of the quard pn-junction and high differential resistance in the breakdown regime, the diodes under test are able to withstand, with no degradation, pulse reverse voltage at least 1600 V.
Authors: Pavel A. Ivanov, Valentin S. Yuferev, Mikhail E. Levinshtein, Jon Q. Zhang, John W. Palmour
Abstract: The resistance of the BJT collector layer can be sharply reduced by the effective injection of minority carriers (holes) from base to collector. As a result, the voltage drop across the BJT becomes substantially lower. The conditions under which this process can occur are the short rise time and the high amplitude of the base pulse.
Authors: Pavel A. Ivanov, Oleg Korolkov, Tat'yana P. Samsonova, Natalja Sleptsuk, Alexander S. Potapov, Jana Toompuu, Toomas Rang
Abstract: In the present paper, 4H-SiC JBS diodes with "boron" p–n junctions have been investigated by means of deep-level transient spectroscopy (DLTS). The sign of the DLTS signal for all the 4H-SiC diodes under study, was positive. The "anomaly" of the DLTS spectra measured is apparently connected with the properties of "boron" p–n junctions. In particular, is presented the role of deep D-centers in recompensation of donors in the JBS diodes.
Authors: Anant K. Agarwal, Pavel A. Ivanov, Michael E. Levinshtein, John W. Palmour, Sergey L. Rumyantsev
Authors: Pavel A. Ivanov, Michael E. Levinshtein, Mykola S. Boltovets, Valentyn A. Krivutsa, John W. Palmour, Mrinal K. Das, Brett A. Hull
Abstract: Forward current-voltage (I-V) characteristics and non-equilibrium carrier lifetime, τ were measured in 4H-SiC pin diodes (10-kV rated, 100 μm base width). The τ value was found to be 3.7 μs at room temperature by measurements of open circuit voltage decay. To the best of the authors' knowledge, the above lifetime value is the highest reported for 4H-SiC. The forward voltage drops were measured to be 3.44 V at current density of 100 A/cm2 and 5.45 V at 1000 A/cm2 showing a very deep modulation of the blocking base by injected carriers. Diodes operated well at elevated temperatures up to 400oC. No essential forward degradation was detected after 300- A×min current stress at 400oC.
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