What is a reverse-conducting IGBT (RC-IGBT)?

A reverse-conducting IGBT (RC-IGBT) integrates an IGBT and a freewheeling diode (FWD) on a single chip. In many IGBT applications, there is a mode in which freewheeling current flows from the emitter to the collector. For this freewheeling operation, the freewheeling diode is connected anti-parallel to the IGBT. Figure (b) shows an example of the internal structure of an RC-IGBT. Part of the P region in the collector electrode is replaced by an N region to form a PIN diode(*1) (P-N--P) with the P region in the emitter electrode. This PIN diode is connected anti-parallel to the IGBT like the FWD shown in Figure (a) and acts as a freewheeling diode. Nowadays, the applications of RC-IGBTs are expanding to the hard-switching fields in addition to voltage resonance.

 (*1) A PIN diode is a diode with a high-resistance intrinsic (I) semiconductor region between P and N regions. Because of low dopant concentration, the intrinsic region has high resistance close to that of an intrinsic semiconductor. The FWD in an IGBT requiring high withstand voltage has this structure.

(a) IGBT+FWD
(a) IGBT+FWD
(b) Example of the internal structure of an RC-IGBT
(b) Example of the internal structure of an RC-IGBT