Integration of heterostructure bipolar transistor and electroabsorption waveguide modulator based on a multifunctional layer design for 1.55 /spl mu/m

An electroabsorption waveguide modulator (EAM) for 1.55 /spl mu/m is embedded into the layer-stack of a heterostructure bipolar transistor (HBT). The collector consists of a complete optical waveguide and enables the monolithic integration of modulators, transistors and also a new merged device to result in a modulator with integrated amplifier. At present this device offers a 3 dB cut-off frequency for optical modulation of 7 GHz and for pure electrical operation cut-off frequencies of f/sub T/ and f/sub max/ both of about 25 GHz.