We investigated the effects of antimony (Sb) overpressure during thermal cleaning (TC) on the surface morphology of InSb substrates using low pressure metalorganic chemical vapor deposition (LP-MOCVD). During the TC process under H-2 ambient, indium (In) droplets were observed inside etch pits on InSb (001) surfaces due to the Sb evaporation from InSb substrates. On the other hand, when InSb substrates were thermally cleaned under trimethylantimony (TMSb) ambient, the formation of In droplets and the etch pits were suppressed, resulting in the smooth lnSb surface. The surface morphology of InSb was dependent on TC temperature. Rough surface morphology was observed at low TC temperature of 435 degrees C and it became smoother with increasing TC temperature. The improvement of surface morphology was caused by the surface stabilization with increasing Sb flux and the increase of adatom migration. The dependence of TMSb flow rate on the surface morphology was also investigated. The TMSb overpressure during the TC of InSb must be maintained to grow high quality InSb epitaxial layers with smooth surface using MOCVD. (C) 2013 Elsevier B.V. All rights reserved,