In this study, an intrinsic hydrogenated amorphous silicon (a-Si:H) thin film was deposited using the plasma-enhanced chemical vapor deposition technique. The samples were annealed at 700 °C and 900 °C for 1 h. Optical measurements indicated the formation of nanocrystallites embedded in an amorphous a-Si:H matrix and the density increased with the annealing temperature. The electrical properties of the Schottky diodes Au/a-Si:H were investigated using admittance spectroscopy over a temperature range of 300–500 K. The conductivity at room temperature in the dark increased by several orders of magnitude after the transition from an amorphous to nanocrystalline structure. The activation energy was deduced based on the variations in the conductivity with temperature. The responses of the amorphous and nanocrystalline phases were identified by complex impedance analysis. The amorphous phase was dominant at low frequencies and high temperatures, whereas the response of the nanocrystalline phase was observed at high frequencies and low temperatures. Semicircular arcs were observed in the impedance plot at different temperatures and an electrical equivalent circuit was proposed. Complex impedance analysis demonstrated that the relaxation phenomenon was a thermally activated process. Moreover, we deduced the temperature at which the available density of the trapped charge states vanished based on the temperature dependence of the average normalized change.