What are RC-IGBTs and IEGTs?

Reverse conductive IGBT : RC-IGBT

• The structure of the RC-IGBT is shown in Fig. 3-16 (a). A diode is formed by making a part of the p-type layer, which is the collector of the IGBT, n-type. This diode has the same function as FWD * 1, which is generally inserted in the IGBT.
• With the introduction of thin wafer technology, it became possible to commercialize this configuration. Since the diode and the IGBT are one chip, it is easy to assemble. Because it is difficult to control the performance of the diode and the IGBT separately, the RC-IGBT is unsuitable for certain applications.

Injection-enhanced gate transistor : IEGT

• Generally, in the high-voltage IGBT, it is difficult to obtain low V_{CE (sat)} characteristics because the carrier concentration of the drift layer (n-type layer) on the emitter side is low.
• The IEGT was developed to obtain low V_{CE (sat)} performance at high withstand voltage (generally 1200 V or higher).
• Fig. 3-16(b) shows the IEGT’s structure and principle.
• It has a trench gate structure. Drawing out of the gate electrode is thinned out.  As a result, carriers are accumulated just under the thinned gate electrode, increasing the carrier concentration on the emitter side.
• This high carrier density decreases resistance of drift layer, and makes V_{CE (sat)} low.