RELIABILITY STUDY OF C-DOPED ALGAAS GAAS HETEROJUNCTION BIPOLAR-TRANSISTORS WITH HALF-MICRON-WIDE EMITTERS/

The reliability of C-doped AlGaAs/GaAs heterojunction bipolar transist ors (HBTs) with emitter widths of 0.5 and 0.8 mu m is studied at base- emitter junction temperatures ranging from 240 degrees C to 290 degree s C with an emitter current density of 1.0 x 10(5) A/cm(2). Although t here is no difference between the initial current-voltage characterist ics of HBTs fabricated using wet etching and dry etching processes, th e bias stress increases the base current of the dry-etched HBTs. The e xcess base current has an ideality factor of two, which indicates that the damage caused during dry etching produces recombination centers d uring minority carrier injection. The activation energy for the curren t gain degradation is found to be 0.89 eV.