Effect of alloy composition on track formation in relaxed Si1-xGex

Strain-relaxed single-crystalline Si1-xGex alloy layers of different compositions (0<xless than or equal to1) were irradiated with 0.7-GeV U ions in the electronic stopping power regime. Transmission electron microscopy reveals extended defects which develop into discontinuous tracks for 0.3less than or equal toxless than or equal to0.8. The defect density and morphology depend significantly on the composition of the alloy, with highest formation probability at xsimilar to0.5. Taking into account the composition dependence of the electron mobility and the mean phonon path in these alloys, the results are discussed within the frame of the thermal-spike approach assuming track melting and imperfect recrystallization. (C) 2003 Elsevier B.V. All rights reserved.