an electro - optic integrated circuit is disclosed wherein the long electrical connections normally present on a large scale integrated circuit are replaced by an optical waveguide layer . a plurality of epitaxial layers are grown on a single substrate and at least three of the plurality of epitaxial layers are grown with bandgaps that are suitable for optical sources , detectors and waveguiding . these primary layers are separated from each other by a barrier layer having a bandgap greater than either of the adjacent primary layers . two of the layers adjacent to the substrate are grown to accommodate electrical devices that can be used to couple electrical signals to the optical source layers and to amplify electrical signals provided by the optical detection layer .