INGAP/GAAS AND INP/INGAAS HETEROJUNCTION BIPOLAR-TRANSISTORS WITH A SUPER HEAVILY CARBON-DOPED BASE GROWN BY METALORGANIC MOLECULAR-BEAM EPITAXY

Metalorganic molecular beam epitaxy (MOMBE) of InP and InGaP was studied by using the elemental group III sources (In and Ga) and tertiarybutylphosphine (TBP) as phosphorus source. The catalysis of heated tantalum (Ta) is important to effectively decompose the TBP. Undoped InGaP with n-type background carrier concentration of n = 4 x 10(15) cm(-3) was obtained, and the controllability of Si doping in InGaP ranging from n = 10(17) to 10(19) cm(-3) was shown by using cracked Si2H6. In the growth of InP with the TBP, carbon was unintentionally incorporated as donor and well controlled in the range suitable for InP/InGaAs HBTs by the growth temperature. The MOMBE growth of InP and InGaP layers was applied to fabricate carbon-doped base InP/InGaAs and InGaP/GaAs HBTs, respectively. Carbon-doped base InP/InGaAs HBTs were fabricated by applying the carbon-doping technique for the InP emitter, and small signal current gain h(fe)=22 and d.c. current gain h(FE)=13 were obtained at J(C) = 0.23 kA/cm(2). The h(fe) = 16 and h(FE) = 12 at a collector current density J(C) = 1.4 kA/cm(2) were also obtained for InGaP/GaAs HBTs having an ultra-high carbon doped base with a hole concentration of 1.5 x 10(21) cm(-3), and a significant degradation of current gain was not observed in reliability measurements under the condition investigated.