With SiGe, who needs GaAs?

The SiGe and GaAs HBTs are compared by analyzing the intrinsic physical properties of the materials and the electrical parameters of these transistors. The comparison is made for devices of comparably advanced structures and of the same design rules. Results showed that the commonly practices SiGe HBT is not really a HBT at all, and that GaAs HBTs are inherently faster than SiGe `HBTs'. GaAs and other compound-semiconductor HBTs will have a place in applications where the higher speed makes an important difference. The inherent advantage of SiGe bipolar transistor over GaAs HBT lies in its being compatible with CMOS VLSI processing.