A significant improvement in electrical characteristics of Schottky diodes designed for X-and-ray detectors has been achieved using semi-insulating CdTe single crystals and unified technology, where both Schottky and near-ohmic contacts were formed by the deposition of the same metal (Ni) on the opposite surfaces of the crystal pre-treated by chemical etching and Ar ion bombardment with different parameters. Reduction of injection of minority carriers from the near-ohmic contact in the neutral part of the diode and high Schottky barrier for holes provides low leakage current even at high bias voltage (50 nA cm 2 at 2000 V and at room temperature). The current-voltage characteristics of the detectors with Ni/CdTe/Ni electrode configuration in the low-voltage range are described by the generation-recombination Sah-Noyce-Shockley theory. The results of the reproducibility and time stability of the fabricated diodes are reported. Index Terms-Charge carrier processes, leakage currents, Schottky diodes, X-and gamma-ray detectors.