Optical devices having integrated waveguide and active areas are realized using a crystallization approach involving the inhibition of defects typically associated with liquid-phase crystalline growth of lattice mismatched materials. According to one example embodiment, a growth region is formed such that the region is isolated from a silicon portion of silicon material. The region extends from a silicon-based seeding area of the substrate. A semiconductor material is deposited on a Silicon-based seeding area and in the growth region. A single crystalline material is formed from the deposited semiconductor material by heating and cooling the deposited semiconductor material while directing growth of the semiconductor material from the Silicon-based seeding area and through an opening sufficiently narrow to mitigate crystalline defects. A light-communicating device is formed by etching the silicon material over an insulator layer and etching the single crystalline material.