Molecular beam epitaxy growth for a heavily-doped thin base layer of heterojunction bipolar transistors used for high-speed integrated circuits

Abstract

The technique of molecular beam epitaxy (MBE) growth has been developed for high-speed AlGaAs/GaAs heterojunction bipolar transistors (HBTs) with a heavily beryllium-doped base layer. Doping limit, DC current gain and reliability were examined under various growth conditions. By the growth under the conditions that substrate temperature was 580°C and V/III flux ratio was 27, the authors have developed HBTs in which the base doping concentration was set to as heavy as 8 × 10 19 cm −3 and the base thickness was set to 45 nm or 90 nm. Using these HBTs, they have fabricated ICs which can operate at 40 GHz.