Ultrashort SiGe Heterojunction Bipolar Transistor-Based High-Speed Optical Modulator

A graded base SiGe HBT optical modulator has high-speed, high optical modulation efficiency, small footprint. In this paper, we present our work in the design and modeling of an HBT optical modulator, its driver circuit and fabrication and integration. A high-efficient HBT electro-optical (EO) modulator with π phase-shift length of 22.6 μm is investigated. The speed of this modulator is calculated to be 30 Gb/s. To verify the functionality of HBT structure as an EO modulator, an 80 Gb/s serializer and driver with an HBT modulator is fabricated by the IBM 8HP BiCMOS process, which has much higher speed but lower modulation efficiency.