InAlAs/InGaAs HBT with superlattice confinement emitter

A 20-period InAlAs/InGaAs superlattice layer was used a hole confinement layer of a heterojunction bipolar transistor (HBT). The SL-HBT exhibits a much smaller offset voltage and a similar current gain when compared to a conventional HBT with a bulk-InAlAs confinement layer. The measured offset voltage and de current gain are 75 (300) mV and 26 (21) in average for a large-area SL-HBT (HEBT). Furthermore, the SL-HBT shows an area-independent current gain. Transistors with emitter dimensions of 150x150, 46x46, 20x20, and 10x10 mu m(2) exhibit current gains in the range of 26 +/- 3. Experimental results reveal that lateral scaling of SL-HBT's is still effective, just like abrupt emitter InAlAs/InGaAs HBT's.