  We demonstrate a monolithic III-V photonic circuit combining a heralded
single photon source with a beamsplitter, at room temperature and telecom
wavelength. Pulsed parametric down-conversion in an AlGaAs waveguide generates
counterpropagating photons, one of which is used to herald the injection of its
twin into the beamsplitter. We use this configuration to implement an
integrated Hanbury-Brown and Twiss experiment, yielding a heralded second-order
correlation $g^{(2)}_{\rm her}(0)=0.10 \pm 0.02$ that confirms single-photon
operation. The demonstrated generation and manipulation of quantum states on a
single III-V semiconductor chip opens promising avenues towards real-world
applications in quantum information.
