Carbonhyphen;doped base GaAs/AlGaAs heterojunction bipolar transistor grown by metalorganic chemical vapor deposition using carbon tetrachloride as a dopant source

摘要

Carbon tetrachloride (CCl4) has been used as a carbon doping source for the base region of a GaAs/AlGaAsNpnheterojunction bipolar transistor (HBT) grown by lowhyphen;pressure metalorganic chemical vapor deposition (MOCVD). Transistors were fabricated and characterized for dc current gain, emitterhyphen;base junction ideality factor, base contact resistance, and external base resistance. Microwave characterization byShyphen;parameter measurement was performed to determine the common emitter current gain and maximum available gain as a function of frequency. Transistors with the base contact area selfhyphen;aligned to a 3times;10 mgr;m emitter finger had a dc current gain as high as 50, an emitterhyphen;base junction ideality factor ofn=1.2, and a current gain cutoff frequency offt=26 GHz. Transistors of equal emitter area without selfhyphen;alignment exhibited dc current gain as high as 86,n=1.2, andft=20 GHz. A base contact resistance ofRc=2.85times;10minus;6OHgr;thinsp;cm2and an external base sheet resistance ofRs=533.4 OHgr;/laplac; were measured. These preliminary results indicate that carbon doping from CCl4may be an attractive substitute for Zn or Mg in GaAs/AlGaAs HBT structures grown by MOCVD.