Integrated quantum photonics relies critically on photon sources that have great purity, single-mode property, scalability, integrability and flexibility for both integrated quantum computing and long-haul quantum communication. Here we report a photon-pair/single-photon source that utilizes cavity-enhanced four-wave mixing in a high-Q silicon microresonator. The photon-pair source has a spectral brightness of 6:25 × 108 pairs/s/mW2/GHz and a quantum cross-correlation of g(2)si (0) = (2:58 ± 0:16) × 104. The generated photons are single-mode, with a quantum self-correlation of 1:87 ± 0:05. The heralded single photons has conditional photon autocorrelation gc(2) as low as 0:0075 ± 0:0017 at 5:9 × 104 pair/s.