A NUMERICAL STUDY OF THE EFFECT OF BASE AND COLLECTOR STRUCTURES ON THE PERFORMANCE OF ALGAAS GAAS MULTI-FINGER HBTS/

A numerical analysis is presented to investigate different base and co llector structures on the d.c. and a.c. performance of AlGaAs/GaAs mul ti-finger heterojunction bipolar transistors (HBTs). The simulation is carried out using a two-dimensional device simulator called MEDICI. F ive possible structures are studied and compared. The results show tha t different structures give rise to different electric fields in the b ase-collector junction and lattice temperatures in the HBT, which cons equently affect the HBT's cutoff frequency and current gain, respectiv ely. The physical mechanisms governing these changes are also discusse d in detail.