Provided is a stable CdZnTe monocrystalline substrate having a small leakage current even when a high voltage is applied and having a lower variation in resistivity with respect to variations in applied voltage values. 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 mass or more and 5.0 ppm by mass or less, wherein the semiconductor wafer has a resistivity of 1.0×107 Ωcm or more and 1.0×108 Ωcm or less when a voltage of 900 V is applied, and wherein a ratio (variation ratio) of the resistivity at application of 0 V to the resistivity at application of a voltage of 900 V is 20% or less.