For future semiconductor devices. germanium layers are very attractive due to their high carrier mobility with ion implantation remaining the dominant method for forming pn junctions Yet, implantation of heavy ions above a critical close causes inadmissible surface toughness and formation of voids To understand the main factors of influence. a comprehensive study on void formation was performed with different ions (BF(2,) P, Al, Ga, Ge, As, Sb) implanted at various doses. dose rates, and energies It was found that the dose is the most important parameter for void formation The critical dose was determined to be 2 . 10(15)cm(-2) for As, 2 . 10(15) cm(-2) for Ga, and 5 10(14) cm(-2) for 5b. respectively For ions with lower mass (BF(2), P, Al), no or only negligible surface roughening was observed. (C) 2009 Elsevier B.V. All rights reserved