High-performance, graded-base AlGaAs InGaAs collector-up heterojunction bipolar transistors using a novel selective area regrowth process

Graded-base AlGaAs/InGaAs collector-up heterojunction bipolar transistors ( C-up HBT's) were successfully fabricated using a novel selective area regro wth process to reduce the base resistance and their de and microwave perfor mances were evaluated. The base is compositionally graded to provide a quas i-built-in field which decreases the base transit time for high-frequency r esponse and increases the base transport factor at low-temperature operatio n. A unity-gain cutoff frequency f(T) = 55 GHz and a maximum frequency of o scillation f(MAX) = 74 GHz for the C-up n-p-n HBT, and an f(r) = 48 GHz and an f(MAX) = 39 GHz for the C-up p-n-p HBT were obtained for devices with a 5-mu m x 10-mu m collector area, The nonself-aligned C-up HBT's reported h ere show great promise for future high-speed C-up complementary bipolar IC' s.