Fabrication of a photonic integrated circuit (PIC) including active elements such as a semiconductor optical amplifier (SOA) and passive elements such as a floating rib waveguide. Selective area doping through ion implantation or thermal diffusion before semiconductor epitaxial growth is used in order to define the contact and lateral current transport layers for each active device, while leaving areas corresponding to the passive devices undoped. InP wafers are used as the substrate which may be selectively doped with silicon.