A WSi base electrode and a heavily-doped thin base layer for high-speed and low-power InGaP/GaAs HBTs

The characteristics of a WSi base electrode and a heavily-doped thin base layer in InGaP/GaAs heterojunction bipolar transistors (HBTs) are demonstrated. An HBT with a new structure using a WSi base electrode and a heavily-doped thin base layer is proposed to achieve high-speed and low-power operation. WSi is shown to be useful in fabricating a base electrode for HBTs with a narrow base-contact width and a buried SiO2 structure, and a contact resistance of under 2 x 10(-7) Omega . cm(2) was obtained with a hole concentration of over 2 x 10(20) cm(-3) by annealing for 30 minutes at 400 degrees C. HBTs with a 30-nm-thick base doped to under 2 x 10(20) cm(-3) achieved current gain of more than 10.