Theoretical and experimental analyses of safe operating area (SOA) of 1200-V 4H-SiC BJT

Int. Rectifier Corp., El Segundo, CA
IEEE Transactions on Electron Devices (Impact Factor: 2.47). 09/2008; 55(8):1887 - 1893. DOI: 10.1109/TED.2008.926682
Source: IEEE Xplore


The safe operating area (SOA) of 1200-V SiC bipolar junction transistor (BJT) is investigated by experiments and simulations. The SiC BJT is free of the second breakdown even under the turn-off power density of 3.7 MW/cm2. The theoretical boundary of reverse-biased SOA caused by the false turn-on is obtained by simulations. The short-circuit capability of the 1200-V SiC BJT is also investigated theoretically and experimentally. Self-heating is considered by the nonisothermal simulation, and 1800-K maximum local temperature is the simulated critical temperature of device failure. The surface condition is very critical for short-circuit capability. From simulations, when the interface trap density increases, the critical temperature decreases. This is believed to be the reason why the experimental results show much shorter short-circuit withstand time than the simulation showed.

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    • "Next to the diode, available SiC device types have included BJTs and JFETs for some time now, and, more recently, SiC Power MOSFETs have also been demonstrated. From an application point of view, to date the BJT is quite a mature technology and its immunity from second breakdown together with recent breakthrough advancements in current gain figures still make it an attractive and competitive candidate for the development of SiC based electrical power conversion systems [3] [4] [5] [6]. Here, tests were carried out on a number of 600 V and 1200V rated SiC transistors and diodes of different manufacturers. "
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    ABSTRACT: There has been a rapid improvement in SiC materials and power devices during the last few years. SiC unipolar devices such as Schottky diodes, JFETs and MOSFETs have been developed extensively and advantages of insertion of such devices in power electronic systems have been demonstrated [1, 2]. However, unipolar devices for high voltage systems suffer from high drift layer resistance that gives rise to high power dissipation in the on-state. For such applications, bipolar devices are preferred due to their low on-resistance. In this article, the physics and technology of SiC bipolar devices, namely Bipolar Junction Transistors (BJTs), Insulated Gate Bipolar Transistors (IGBTs), and Gate Turn Off Thyristors (GTOs), are discussed. A detailed review of the current status and future trends in these devices is given with an emphasis on the device design and characterization. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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    ABSTRACT: Silicon as a semiconductor material is well established and first choice for the vast majority of devices. However, due to continuous device optimisation and improvements in the production process, the material properties are more and more the limiting factor. Workarounds like the super junction stretch the limits but usually at substantial cost. So a lot of effort is spent into the more straight forward approach, i.e. changing the semiconductor material. For power devices, wide band-gap semiconductors are most attractive because of low conduction and switching losses, high temperature capability, and high thermal conductivity. Despite some material and process issues back then, the first wide band-gap device, a silicon carbide Schottky-diode, was commercialised eight years ago and found a reasonable market niche. In the meantime significant progress has been made in terms of material quality and cost. However, the silicon carbide Schottky-diode is still the only wide band-gap device on the market and, in particular, there is no wide band-gap switch commercially available yet. Of course, the material cost is still two orders of magnitude higher than for silicon and there are still some material defects that lead to degradation of bipolar devices, but in general the material quality and wafer size is no longer a road block on the way to commercialisation of further devices and the device concepts are there also. So it became rather an economical than a technological question - and silicon is a strong competitor, as the case of the super junction MOSFET shows. On the other hand silicon is not just a competitor but also a strong ally, when it comes to the development of packaging suited for higher operation temperatures, frequencies, and switching speeds. So at the end the question remains: Which additional wide band-gap devices will be able to find and sustain their respective market positions?
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