Fig. 1: Fully integrated photonic platforms.

a, The evolution of fully integrated photonic platforms: pure III–V platform relies on multiple epitaxial regrowths to combine active and passives structures; heterogeneous III–V on SOI requires two bonding procedures, the ‘smart-cut’ method to produce an integrated Si film and III–V bonding to transfer III–V epitaxy layers from native substrate onto SOI; the heterogeneous III–V on SiN platform needs only SiN direct deposition to integrate SiN film, and only one wafer bonding process to add the III–V layer. b, The spectral coverage of fully integrated PICs: boxes represent the transparency window of passive platforms on the basis of different materials (InP⁵², GaAs⁵³, Si^54,55, SiN^22,24,56) that can be used for fully integrated PICs, points represent the current state-of-the-art loss on these passive waveguides and wafer marker sizes represent the current maximum wafer scale in foundries. The icons on the upper side represent applications of fully integrated PICs over the spectrum map. Purple icons indicate applications accessible to both existing fully integrated PICs and the III–V/SiN platform of this article; blue icons correspond to applications made possible by the heterogeneous III–V/SiN platform.