Novel Design of SOI SiGe HBTs with High Johnson's Figure-of-Merit

A novel design of SOI SiGe HBTs with a buried n
⁺
thin layer and p
^-
doping layer is proposed to improve the product of cutoff frequency and breakdown voltage, which is a vital Johnson's figure of merit (J-FOM) of the device. In this design, the n
⁺
thin layer is used to increase the cutoff frequency and the p
^-
doping layer is adopted to maintain a high breakdown voltage. Furthermore, the thickness of n
⁺
thin layer is also studied to improve the J-FOM. As a result, for the novel SOI SiGe HBT, the J-FOM is increased from 351.5GHz-V to 482.3GHz-V, when compared with that of the traditional device. This design effectively develops the application of SOI SiGe HBTs in microwave power.