Antimonide-based field-effect transistors and heterojunction bipolar transistors grown by molecular beam epitaxy

摘要

For the development of novel high-speed devices, the epitaxial growth of antimonide-based compounds and devices, including field effect transistors (FETs) and hetero-junction bipolar transistors (HBTs), was explored using gas-source molecular beam epitaxy (MBE). The first and second parts of the dissertation detail the growth of InAsSb and InGaSb as the channel materials for n- and p-type FETs, respectively. Both compounds were grown metamorphically on InP substrates with a composite AlSb/AlAs0.5Sb0.5 buffer layer, which was proved to be effective in enhancing the epitaxial quality. By optimizing the growth conditions, the intrinsic carrier mobilities of n-type InAsSb and p-type pseudomorphic InGaSb quantum wells could reach 18000 and 600 cm2/V-s at room temperature, respectively. InAsSb FET showed a high transconductance of 350 mS/mm, which indicated the high potential in the high-speed applications. The third part of the dissertation describes the modification of the emitter-base junction of ultra-fast type-II GaAsSb-based HBTs in order to eliminate the carrier blocking and enhance the current gain. InAlP was used to replace the InP emitter and form a type-I emitter-base junction. Results for large devices show that this modification could improve DC current gain from 80 to 120. The results indicate that type-I/II InAlP/GaAsSb HBTs are promising to achieve better radio-frequency (RF) performance with higher current driving capability.