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 2×10-7 Ω· cm2 was obtained with a hole concentration of over 2×1020 cm-3 by annealing for 30 minutes at 400° C. HBTs with a 30-nm-thick base doped to under 2×1020 cm-3 achieved current gain of more than 10.