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.