There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Wide bandgap semiconductors show superior material properties enabling potential power device operation at higher temperatures, voltages, and switching speeds than current Si technology. As a result, a new generation of power devices is being developed for power converter applications in which traditional Si power devices show limited operation. The use of these new power semiconductor devices will allow both an important improvement in the performance of existing power converters and the development of new power converters, accounting for an increase in the efficiency of the electric energy transformations and a more rational use of the electric energy. At present, SiC and GaN are the more promising semiconductor materials for these new power devices as a consequence of their outstanding properties, commercial availability of starting material, and maturity of their technological processes. This paper presents a review of recent progresses in the development of SiC- and GaN-based power semiconductor devices together with an overall view of the state of the art of this new device generation.

A Survey of Wide Bandgap Power Semiconductor Devices

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Art of electronics

Journal of Applied physics,Vol.33 : 1962年に発表されたレオロジー関連の論文

Semiconductor Power Devices

The reverse recovery destruction limit of 3.3 kV fast recovery diodes was investigated by measurements and device simulations. Based on a good agreement between the measured destruction limit and current filamentation in simulations, it is proposed that the destruction is triggered by the onset of impact ionization at the n-n/sup +/ junction. The proposed destruction mode has significant similarities with previously described second breakdown at the static breakdown voltage. An approximate analytical model which was derived indicates that avalanche at the n-n/sup +/ junction should become unstable with a time constant on the order of nanoseconds, whereas dynamic avalanche at the p-n junction should be stable. Simulations and measurements show that the reverse recovery safe operating area depends on the n-base width. An approximate equation is proposed to determine the minimum n-base width required for a nondestructive reverse recovery with dynamic avalanche as a function of the reverse peak voltage.

On the destruction limit of Si power diodes during reverse recovery with dynamic avalanche

In this brief, the electrical performance in terms of maximum current gain and breakdown voltage is compared experimentally and by device simulation for 4H-SiC BJTs passivated with different surface-passivation layers. Variation in bipolar junction transistor (BJT) performance has been correlated to densities of interface traps and fixed oxide charge, as evaluated through MOS capacitors. Six different methods were used to fabricate SiO2 surface passivation on BJT samples from the same wafer. The highest current gain was obtained for plasma-deposited SiO2 which was annealed in N2O ambient at 1100°C for 3 h. Variations in breakdown voltage for different surface passivations were also found, and this was attributed to differences in fixed oxide charge that can affect the optimum dose of the high-voltage junction-termination extension (JTE). The dependence of breakdown voltage on the dose was also evaluated through nonimplanted BJTs with etched JTE.

Surface-Passivation Effects on the Performance of 4H-SiC BJTs

Epitaxial Ti3SiC2 (0001) thin film contacts were grown on doped 4H-SiC (0001) using magnetron sputtering in an ultra high vacuum system. The specific contact resistance was investigated using linea ...

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Ohmic contact properties of magnetron sputtered Ti3SiC2 on n- and p-type 4H-silicon carbide

Implantation-free mesa-etched 4H-SiC PiN diodes with a near-ideal breakdown voltage of 4.3 kV (about 80% of the theoretical value) were fabricated, measured, and analyzed by device simulation and optical imaging measurements at breakdown. The key step in achieving a high breakdown voltage is a controlled etching into the epitaxially grown p-doped anode layer to reach an optimum dopant dose of ~ 1.2 times 1013 cm-2 in the junction termination extension (JTE). Electroluminescence revealed a localized avalanche breakdown that is in good agreement with device simulation. A comparison of diodes with single- and double-zone etched JTEs shows a higher breakdown voltage and a less sensitivity to varying processing conditions for diodes with a two-zone JTE.

High-Voltage 4H-SiC PiN Diodes With Etched Junction Termination Extension

Accurate physical modeling has been developed to describe the current gain of silicon carbide (SiC) power bipolar junction transistors (BJTs), and the results have been compared with measurements. Interface traps between SiC and SiO2 have been used to model the surface recombination by changing the trap profile, capture cross section, and concentration. The best agreement with measurement is obtained using one single energy level at 1 eV above the valence band, a capture cross section of 1 × 10-5 cm2, and a trap concentration of 2 × 1012 cm-2. Simulations have been performed at different temperatures to validate the model and characterize the temperature behavior of SiC BJTs. An analysis of the carrier concentration at different collector currents has been performed in order to describe the mechanisms of the current gain fall-off at a high collector current both at room temperature and high temperatures. At room temperature, high injection in the base (which has a doping concentration of 3 × 1017 cm-3) and forward biasing of the base-collector junction occur simultaneously, causing an abrupt drop of the current gain. At higher temperatures, high injection in the base is alleviated by the higher ionization degree of the aluminum dopants, and then forward biasing of the base-collector junction is the acting mechanism for the current gain fall-off. Forward biasing of the base-collector junction can also explain the reduction of the knee current with increasing temperature by means of the negative temperature dependence of the mobility.

Martin Domeij

Papers

On the destruction limit of Si power diodes during reverse recovery with dynamic avalanche

Surface-Passivation Effects on the Performance of 4H-SiC BJTs

Ohmic contact properties of magnetron sputtered Ti3SiC2 on n- and p-type 4H-silicon carbide

High-Voltage 4H-SiC PiN Diodes With Etched Junction Termination Extension

Modeling and Characterization of Current Gain Versus Temperature in 4H-SiC Power BJTs