The emitter-base interface current in silicon bipolar transistors with emitters deposited by plasma-enhanced CVD

The DC characteristics of bipolar devices with emitters deposited by the glow discharge of silane are discussed. The emitter material can be amorphous or single crystalline, grown by low-temperature plasma epitaxy. At deposition temperatures as low as 320 degrees C, surface cleaning is the most critical step in the process. Results on different ex-situ and in-situ cleanings are included. A model for the base current of bipolar transistors which is in agreement with the observations is proposed. It is shown that the base-emitter interface limits the transistor performance. After optimization, diode ideality factors approaching unity are obtained.>