2‐K photoluminescence was used to determine the amount of nonuniformity present in undoped semi‐insulating GaAs bulk substrate materials grown by the liquid‐encapsulated Czochralski method. The relative photoluminescence intensities of the intracenter (5T2−5E) transition of the Fe2+state, the near‐band‐edge transitions, and the Zn peaks, measured across the wafer diameter, show almost the same ‘‘W’’ pattern. The deep‐center bands at 0.63 and 0.77 eV were also measured. Possible mechanisms of the photoluminescence intensity variation are discussed. In the materials used, a predominant shallow acceptor was observed to be Zn.