Abstract: A composite integrated optical device includes a substrate including a silicon layer and a waveguide disposed in the silicon layer. The composite integrated optical device also includes an optical detector bonded to the silicon layer and a bonding region disposed between the silicon layer and the optical detector. The bonding region includes a metal-assisted bond at a first portion of the bonding region. The metal-assisted bond includes an interface layer positioned between the silicon layer and the optical detector. The bonding region also includes a direct semiconductor-semiconductor bond at a second portion of the bonding region.