  We have realised laser-doped all-silicon superconducting (S)/ normal metal
(N) bilayers of tunable thickness and dopant concentration. We observed a
strong reduction of the bilayers critical temperature when increasing the
normal metal thickness, a signature of the highly transparent S/N interface
associated to the epitaxial sharp laser doping profile. We extracted the
interface resistance by fitting with the linearised Usadel equations,
demonstrating a reduction of one order of magnitude from previous
superconductor/doped Si interfaces. In this well controlled crystalline system
we exploited the low resistance S/N interfaces to elaborate all-silicon lateral
SNS Josephson junctions with long range proximity effect. Their dc transport
properties, such as the critical and retrapping currents, could be well
understood in the diffusive regime. Furthermore, this work lead to the
estimation of important parameters in ultra-doped superconducting Si, such as
the Fermi velocity, the coherence length, or the electron-phonon coupling
constant, fundamental to conceive an all-silicon superconducting electronics.
