Preventing instability damages in multiple finger heterojunction bipolar transistors by tunnel diode emitter design

We present a tunnel diode emitter structure capable of preventing instability damage in multiple finger high power heterojunction bipolar transistors. An Esaki diode pair vertically integrated to the wide bandgap emitter self-limits the finger current and prevents current runaway. We describe the principle of operation and demonstrate the electrical characteristics of a single finger in the proposed device.