MOMBE growth of InGaP with tertiarybutylphosphine (TBP) and its application to the carbon-doped base InGaP/GaAs HBTs

Tertiarybutylphosphine (TBP), which is a promising substitute for phosphine (PH₃), was used for the growth of In_0.5Ga_0.5P by metalorganic molecular beam epitaxy (MOMBE) with elemental In and Ga as group III sources. In the decomposition of TBP, the catalysis by heated Ta is important to obtain high quality In_0.5Ga_0.5P layers as compared with the case of only pyrolysis. We modified the cracking cell for TBP to the new one by including Ta sheet and shots inside the PBN crucible, and undoped In_0.5Ga_0.5P with n-type background carrier concentrations of ~4×10¹⁵ cm^-3 was obtained. Electron concentrations ranging from 10¹⁷ to 10¹⁹ cm^-3 were successfully controlled by using cracked Si₂ H₆ as n-type dopant source. The MOMBE growth of In_0.5Ga_0.5P layers was applied to carbon (C)-doped base In_0.5Ga_0.5P/GaAs heterojunction bipolar transistors (HBTs) with high hole concentrations in the base. Common emitter current gain (h_fe) of 28 at J_c=1.1 kA/cm ² was obtained for HBTs with the hole concentration in the C-doped GaAs base of 1×10²⁰ cm^-3