I've been looking at IGBTs for a power project. Primarily since they can handle high voltage and have decent reverse blocking capabilities. Two devices I'm familiar with are Punch Through (PT) and Non-Punch Through (NPT). A third one was offered a few years ago (I can only find one vendor who sells the device) but has since been deemed obsolete. This particular device was called the "reverse blocking IGBT" or RB-IGBT. It had blocking diode that would allow for a more robust reverse Vce breakdown (the semiconductor structure of the RB-IGBT was similar to a NPT, but RB has the p+ layer (connected to the emitter) actually encapsulates the entire device up the oxide as if the p+ layer acted as a bucket). Seemed to me that the RB would be a better device for AC operations than an NPT. So, what happened? Or did they come up with a better, cheaper NPT device? Or did I miss something obvious?
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1\$\begingroup\$ Doesn't sound any different than what happens to any niche variant of a device, like double gate MOSFETs or Gate Turn Off Thyristors. There was also funny device I can't quite remember that I think was like a BJT with some other transistor in series with its source and was meant to keep it just out of saturation or something like that for faster switching. I can't quite remember. Does this RB-IGBT accomplish anything that a regular IGBT with a series diode cannot? Because reading around it sounds like it can't, which would explain why you can't find one. \$\endgroup\$– DKNguyenCommented Feb 6, 2020 at 5:05
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\$\begingroup\$ GTOs weren't niche, they were very mainstream back in the days, they were just replaced by better devices (power MOSFETs and IGBTs) \$\endgroup\$– Ken GrimesCommented Feb 6, 2020 at 11:13
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\$\begingroup\$ @KenGrimes Were they? You would think thyristors would have died out while GTOs would have stuck around. Why are GTOs gone but thyristors not? I guess because the main use now is AC where you can get away with thyristors and GTOs are not needed? \$\endgroup\$– DKNguyenCommented Feb 6, 2020 at 15:52
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\$\begingroup\$ @DKNguyen you're right that GTOs are gone now, my point was that they were not a niche application of Thyristors, they were essential and very broadly used in all cases were you need to control when to turn off (inverters in the 70s). Of course they have now been displaced by power MOSFETs and IGBTs \$\endgroup\$– Ken GrimesCommented Feb 6, 2020 at 16:27
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1\$\begingroup\$ @DKNguyen There was also funny device I can't quite remember that I think was like a BJT with some other transistor in series with its source Yes, this is the cascode connected BJT with MOSFET in its emitter. ST brought out a single component with this configuration called Emitter switched bipolar transistor. Sold for just a few years then was obsoleted. \$\endgroup\$– Fabio BaroneCommented May 28 at 19:45
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I imagine it has to with costs and volume production. To make power transistors competitive they need to be mass produced and reverse blocking capability is just not the main use of an IGBT. IGBTs main use is as a switch in a three phase inverter, and there you don't need a RB-IGBT. Nowadays IGBT are being replaced by SiC-MOSFETs in the 600 V-1200 V market, so I expect that IGBT manufacturers will not innovate much more either.
PS:PT and NPT refer to how the electric field inside the device behaves, that doesn't imply capability to block voltage in third quadrant operation
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\$\begingroup\$ Per your PS. I was referring to Figure 4 of this link. I don't fully understand why there would be a difference between the two devices electric field wise, unless punch-through occurs first along the left and right edges of the left diagram as a result of the geometry. \$\endgroup\$ Commented Feb 6, 2020 at 19:16
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\$\begingroup\$ You can check chapter 10 of "Semiconductor Power Devices Physics, Characteristics, Reliability" from Lutz, Schlangenotto, Scheuermann and De Doncker or chapter 2 from "Insulated Gate Bipolar Transistor IGBT Theory and Design" from Khanna for instance. Oterwise you might want to open a new question, I can't add images to a comment and I need an image to explain it :) \$\endgroup\$ Commented Feb 7, 2020 at 8:22