  High-efficient and high-purity photon sources are highly desired for quantum
information processing. We report the design of a chip-scale hybrid SixNy and
thin film periodically-poled lithium niobate waveguide for generating
high-purity type-II spontaneous parametric down conversion (SPDC) photons in
telecommunication band. The modeled second harmonic generation efficiency of
225% W^(-1)*cm^(-2) is obtained at 1560nm. Joint spectral analysis is performed
to estimate the frequency correlation of SPDC photons, yielding intrinsic
purity with up to 95.17%. The generation rate of these high-purity photon pairs
is estimated to be 2.87 * 10^7 pairs/s/mW within the bandwidth of SPDC. Our
chip-scale hybrid waveguide design has the potential for large scale on-chip
quantum information processing and integrated photon-efficient quantum key
distribution through high-dimensional time-energy encoding.
