The super junction bipolar transistor: a new silicon power device concept for ultra low loss switching applications at medium to high voltages

Abstract

A new silicon power device concept based on the super junction (SJ) principle for power electronics in a broad spectrum of consumer, industrial and other energy conversion applications is presented in this paper. This new concept can help to sustain the trend towards ultra low loss switching––the past, present and future dominant driving force in the development of silicon high power switches. The super junction bipolar transistor (SJBT) shares many similarities with the super junction MOSFET. It has a similar MOS control structure integrated on the cathode side on top of a base region, which is organized into a columnar structure of alternating p- and n-doped pillars. The anode consists of a p-doped emitter––the SJBT is thus a bipolar super junction power device with carrier modulation taking place in only some portion of the base. The super junction structure makes up for fundamentally different device characteristics compared to an IGBT: carrier modulation in the SJBT is made possible by elimination of the reverse bias between p- and n-doped pillars when large quantities of majority carriers are injected from the p-emitter into the p-type pillar. With the electrostatic potential being grounded at the cathode, de-biasing of the pillars as well as carrier modulation will vanish towards the cathode. The unique characteristic of the SJBT on-state is an electron–hole plasma originating at the anode, which will segregate and give place to unipolar current flow in both pillars (de-mixing of the plasma) in the base region close to the cathode. Compared to an IGBT, the SJBT offers the same or lower conduction losses at a very small fraction (25%) of the cost in terms of switching losses.