GROWTH OF 100 GHZ SIGE-HETEROBIPOLAR TRANSISTOR (HBT) STRUCTURES

The transit frequency f(T) of SiGe-heterobipolar transistors (HBT's) w as increased from 20 GHz to 100 GHz. This was mainly achieved by thick ness reduction of the double heterojunction SiGe-base from 65 nm to 25 nm. The complete vertical structure of the SiGe-HBT's (collector, bas e, emitter, emitter contact) was grown in one run by Si molecular beam epitaxy (Si-MBE). The growth temperature was varied from 650-degrees- C at the collector side to 325-degrees-C at the emitter contact side. The different n-type doping levels (10(17)/cm3, 10(18)/cm3, 10(20)/cm3 ) were obtained by applying three different Sb-doping techniques (seco ndary implantation, adatom pre build-up, low temperature doping). The p-type base was doped with boron. The doping level in the base (6 X 10 (19)/cm3) exceeded the emitter doping level by a factor of 30 (doping level inversion).