Bistability and hysteresis in the characteristics of segmented-anode lateral IGBTs

The voltage- and current controlled bistability of Segmented Anode Lateral IGBTs (SA-LIGBT) containing more than one p-anode segment has been investigated experimentally by means of monitoring the infrared recombination radiation, as well as theoretically by two-dimensional device simulation. We have found out that the instabilities are caused by the switching of single p-anode segments from the MOS-mode into the conductivity modulated state and vice-versa. The switching current and voltage show pronounced memory effects, if the single cell structure exhibits S-type Negative Differential Conductivity (SNDC) because of conductivity modulation. The simulation of a simplified vertical hybrid diode/pnp-transistor structure shows very good qualitative agreement with measured characteristics and carrier distributions in the SA-LIGBT. Generally, such hysteresis effects may occur in all electronic devices containing SNDC-elements switched in parallel.