Ge epilayer with low dislocation density is prepared on a low temperature self-patterned Ge coalescence island template on Si substrate by ultra-high vacuum chemical vapor deposition. The depth profile of dislocation density in the Ge epilayer measured by etch-pit counting indicates that the dislocation density decreases drastically when the thickness of Ge layer is larger than 270 nm, and then depends weakly on the further increase of Ge thickness. The reduction of dislocations is ascribed to the Ge islands coalescence and lateral growth during deposition of Ge at higher temperature. 1.05-mu m-thick Ge epilayer on Si with a dislocation density of the order of 10(6)cm(-2) and root-mean-square surface roughness of 0.45 nm are achieved without any additional thermal treatments. (C) 2011 Elsevier B.V. All rights reserved.