Frequency response improvement of 120 GHz fT SiGe HBT by optimizing the contact configurations

For characterizing the frequency and power response of the SiGe HBT devices, the HBT devices with different base and collector contact configuration structure have been fabricated by using the 0.18 μm high-speed SiGe BiCMOS technologies. In this work, we investigated three different types of layout with the same emitter area A_E=0.3×10.16 μm², including single base and single collector contact, double base and single collector contacts, and double base and double collector contacts. Regarding the maximum output power and cutoff frequency (f_T), the double bases and double collectors structure is the optimized layout, which provides a 6.4 dBm maximum output power and a PAE of 40 % at 2.4 GHz. It also leads to achieve a higher cutoff frequency due to the reduction of contact resistances.