Millimetre-wave slow wave electrodes on InP are realised by capacitive
ly loading of coplanar waveguide (CPW) transmission lines using interd
igitated metal-semiconductor-metal (MSM) structures. The slow wave str
uctures are designed for velocity matching with InP-based optical wave
guides and a 50 Omega line impedance. Their dispersion, loss and imped
ance characteristics are measured up to 40GHz, and they demonstrate th
e suitability of the lines for use in distributed MSM photodetectors.