The low‐frequency resistance noise of proton‐irradiatedn‐GaAs epitaxial layers was studied at temperatures from 77 to 300 K. Two types of 1/f noise were identified from the temperature dependence of the 1/f noise parameter &agr;. One type of 1/f noise that is dominating at high temperatures seems to be of intrinsic origin related to lattice phonon scattering. The other dominating one at lower temperatures is, then, of extrinsic origin induced by the irradiation. The extrinsic type of 1/f noise is consistent with the quantum ‘‘local‐interference’’ effect and can reasonably be described by the Dutta–Dimon–Horn model [P. Dutta and P. M. Horn, Rev. Mod. Phys.53, 497 (1981)].