We measured terahertz (THz) radiation from GaAs (1 0 0) surface coated with rough Au film in the thickness ranging from 5 to 21nm under the incident angle from 0 to 50. Anomalous THz emission was observed with inhomogeneous crack structures at normal incidence, which originates dominantly from the lateral photo-Dember current. Meanwhile, enhanced THz radiation from Au/GaAs was investigated with the variation of the Au morphology, which confirmed that localized surface plasmons play an important role in the THz radiation. The results indicate the prospect of harnessing surface plasmons for efficient THz emission with controllable morphology of Au on semiconductors. (C) 2013 Elsevier B.V. All rights reserved.