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Semi‐insulating freestanding GaN substrates were produced by hydride vapor phase epitaxy using intentionally introduced iron impurity atoms to compensate residual donors in GaN. Variable temperature resistivity measurements determined the resistivity of an iron‐doped GaN sample to be ∼3 × 10⁵ Ω cm at 250 °C. The activation energy of the carrier was 0.51 eV and room temperature resistivity was determined to be ∼2 × 10⁹ Ω cm at room temperature by linear fitting and extrapolation to room temperature. Near‐infrared photoluminescence at 1.6 K exhibited sharp emission at 1.3 eV, associated with the ⁴T₁(G) →⁶A₁(S) internal transition of the Fe³⁺ charge state. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)