Electric transport in the phase-slip-free superconducting epitaxial Nb(Ti)N sub-micron structures

•This manuscript presents investigation of the current-voltage characteristics of phase-slip-free NbN nanostructured superconducting single photon detector (SNSPD) as a function of temperature and applied magnetic field.•Presented results are compared with data received for phase-slip-free submicron-wide single bridge NbTiN structure.•Our data demonstrate essential physical difference in transport properties and in curvature of current-voltage curves for this structures.