Provided is a CdZnTe monocrystalline substrate which has a small leakage current even when a voltage is applied from a low voltage to a high voltage, and which has a lower variation in resistivity with respect to applied voltage changes from 0 to 900 V, and which can maintain a stable resistivity. A semiconductor wafer comprising a cadmium zinc telluride monocrystal having a zinc concentration of 4.0 at % or more and 6.5 at % or less and a chlorine concentration of 0.1 ppm by weight or more and 5.0 ppm by weight or less, wherein when a voltage is applied in a range of from 0 to 900 V, the semiconductor wafer has a resistivity for each applied voltage value of 1.0×107 Ωcm or more and 7.0×108 Ωcm or less, and wherein a relative variation coefficient of each resistivity to the applied voltages in a range of from 0 to 900 V is 100% or less.