Phosphorus-doped high-resistivity silicon from different vendors and production series has been used to fabricate diodes in the same process run. The diodes were investigated by capacitance-voltage, current-voltage and deep level transient spectroscopy (DLTS) measurements with the intention to evaluate the quality variation of silicon diodes due to the starting material. The leakage current measurements showed that the average leakage current at full depletion was ∼ 5 times larger in the worst wafer compared to the best. The wafers were divided into two batches which received two different segregation annealings. It was observed that the improvement in the average leakage current due to long versus short segregation annealing varied substantially between wafers.