  Advances in quantum photonics have shown that chip-scale quantum devices are
translating from the realm of basic research to applied technologies. Recent
developments in integrated photonic circuits and single photon detectors
indicate that the bottleneck for fidelity in quantum photonic processes will
ultimately lie with the photon sources. We present and demonstrate a silicon
nanophotonic chip capable of emitting telecommunication band photon pairs that
exhibit the highest raw degree of time-energy entanglement from a
micro/nanoscale source, to date. Biphotons are generated through
cavity-enhanced spontaneous four-wave mixing (SFWM) in a high-Q silicon
microdisk resonator, wherein the nature of the triply-resonant generation
process leads to a dramatic Purcell enhancement, resulting in highly efficient
pair creation rates as well as extreme suppression of the photon noise
background. The combination of the excellent photon source and a new phase
locking technique, allow for the observation of a nearly perfect coincidence
visibility of (96.6 $\pm$ 1.1)$\%$, without any background subtraction, at a
large pair generation rate of (4.40 $\pm$ 0.07) $\times$ 10$^5$ pairs/s.
