A monolithically integrated silicon modulator with a 10 Gb/s 5 Vpp or 5.6 Vpp driver in 0.25 ??m SiGe:C BiCMOS

摘要

This paper presents as a novelty a fully monolithically integrated 10Gb/s silicon modulator consisting of an electrical driver plus optical phase modulator in 0.25µm SiGe:C BiCMOS technology on one chip, where instead of a SOI CMOS process (only MOS transistors) a SiGe BiCMOS process (MOS transistors and fast SiGe bipolar transistors) is implemented. The fastest bipolar transistors in the BiCMOS product line used have a transit frequency of 120GHz and a collector-emitter breakdown voltage of 2.2V (IHP SG25H3). The main focus of this paper will be given to the electronic drivers, where two driver variants are implemented in the test chips. Circuit descriptions and simulations, which treat the influences of noise and bond wires, are presented. Measurements at separate test chips for the drivers show that the integrated driver variant one has a low power consumption in the range of 0.66W to 0.68W but a high gain of S21=37dB. From the large signal point of view this driver delivers an inverted as well as a non-inverted output data signal between 0V and 2.5V (5Vpp differential). Driver variant one is supplied with 2.5V and with 3.5V. Bit-error-ratio (BER) measurements resulted in a BER better than 10E-12 for voltage differences of the input data stream down to 50mVpp. Driver variant two, which is an adapted version of driver variant one, is supplied with 2.5V and 4.2V, consumes 0.83W to 0.87W, delivers a differential data signal with 5.6Vpp at the output and has a gain of S21=40dB. The chip of the fully integrated modulator occupies an area of 12.3mm^2 due to the photonic components. Measurements with a 240mVpp electrical input data stream and for an optical input wavelength of 1540nm resulted in an extinction ratio of 3.3dB for 1mm long RF phase shifters in each modulator arm driven by driver variant one and a DC tuning voltage of 1.2V. The extinction ratio was 8.4dB at a DC tuning voltage of 7V for a device with 2mm long RF phase shifters and driver variant two.