Single-pulse observation of photoemission during avalanche breakdown in insulated gate bipolar transistor

Abstract

Under unclamped inductive switching (UIS) condition, the distribution of avalanche breakdown current in insulated gate bipolar transistor (IGBT) is non-uniform. Many previous studies have shown the results of calculating current distribution and behavior using a device simulator. As a result of experimental observation, there are some reports that the temperature change of the device was observed by using infrared thermography. However, previous observational experiments had been conducted in only a few microseconds of time resolution. In order to understand the behavior of current concentration (filament) related to the breakdown of IGBTs, a method with a sub-microsecond time resolution and high sensitivity that can be observed even under single avalanche breakdown condition is required. In this study, we observed the photoemission associated with the avalanche breakdown current in IGBTs using a multi-anode photomultiplier tube (PMT) with a high temporal resolution of 20 ns. Since PMT can detect extremely weak light, it is possible to observe photoemission even under a single pulse bias condition. The increase and decrease and the movement of the light emitted from the current filament were observed. It was found that it changed every time the pulse was applied.