The surfactant effects of tellurium on GaAs hornoepitaxy were studied by introducing diethyltelluride (DETe) during growth on (0 0 1) patterned substrates. The DETe partial pressure was systematically varied from 0 to 2.9 x 10(-4) Torr. An impurity concentration of 9.0 x 10(18) cm(-3) was estimated from 4-point probe measurements for the sample grown with the highest DETe flow rate. The presence of Te on the growing surface had no detectable effect on the lateral growth rates of the patterned mesas, but had a dramatic effect on the evolution of the mesa profiles and the surface morphology. The surfactant Te reduced the rms toughness from 5 to 0.5 nm, produced trenches and pits on the surface, and caused an increase in the sidewall angles of pits, trenches, and patterned mesas. The increase in sidewall angle is consistent with "slope selection" theory, and correlates to an increase in the Ehrlich-Schwoebel (ES) barrier. Kinetic simulations support the hypothesis that increased sticking at steps and an increased ES barrier are the mechanisms by which tellurium changes the surfaces morphology. (C) 2004 Elsevier B.V. All rights reserved.