Intimate integration of photonics with electronics is regarded as the key to further improvement in bandwidth, speed and energy efficiency of information transport systems. Here, a method based on wafer-scale polymer bonding is reviewed which is compatible with foundry-sourced high-performance InP photonics and BiCMOS electronics. We address challenges with respect to circuit architecture, co-simulation framework and interconnect technology and introduce our approach that can lead to broadband high-density interconnects between photonics and electronics. Recent proof-of-concept work utilizing DC-coupled driver connections to modulators, which significantly reduces the interconnect complexity, is summarized. Furthermore, co-simulation concepts based on equivalent circuit models are discussed with emphasis on the importance of impedance matching between driver and modulator. Finally, realizations of broadband interconnects and functional photonic building blocks after wafer bonding are highlighted to demonstrate the potential of this wafer-scale co-integration method.