MOLECULAR-BEAM EPITAXY GROWTH FOR A HEAVILY-DOPED THIN BASE LAYER OF HETEROJUNCTION BIPOLAR-TRANSISTORS USED FOR HIGH-SPEED INTEGRATED-CIRCUITS

The technique of molecular beam epitaxy (MBE) growth has been develope d for high-speed AlGaAs/GaAs heterojunction bipolar transistors (HBTs) with a heavily beryllium-doped base layer. Doping limit, DC current g ain and reliability were examined under various growth conditions. By the growth under the conditions that substrate temperature was 580 deg rees 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 x 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.