  The compact size, scalability, and strongly confined fields in integrated
photonic devices enable new functionalities in photonic networking and
information processing, both classical and quantum. Gallium phosphide (GaP) is
a promising material for active integrated photonics due to its high refractive
index, wide band gap, strong nonlinear properties, and large acousto-optic
figure of merit. In this work we demonstrate that silicon-lattice-matched
boron-doped GaP (BGaP), grown at the 12-inch wafer scale, provides similar
functionalities as GaP. BGaP optical resonators exhibit intrinsic quality
factors exceeding 25,000 and 200,000 at visible and telecom wavelengths
respectively. We further demonstrate the electromechanical generation of
low-loss acoustic waves and an integrated acousto-optic (AO) modulator.
High-resolution spatial and compositional mapping, combined with ab initio
calculations indicate two candidates for the excess optical loss in the visible
band: the silicon-GaP interface and boron dimers. These results demonstrate the
promise of the BGaP material platform for the development of scalable AO
technologies at telecom and provide potential pathways toward higher
performance at shorter wavelengths.
