The combined use of Rutherford backscattering spectrometry and secondary ion mass spectroscopy allowed a complete characterization of a set of SiGe relaxed buffer layers grown by low-energy plasma-enhanced chemical vapor deposition. The Ge contents for the top SiGe constant composition layers have been obtained by RBS. Matrix effects have been studied by using monoatomic and biatomic ions as well as low and high energy O-2(+) and Cs+ primary beam ions. We show that matrix effects are suppressed when an O-2(+) primary beam ion source is used at 3 keV, and when detecting with Si-30(+) and Ge-70(+) secondary ions for Ge contents < 0.47. For higher Ge contents a better compromise is achieved with Cs+ bombardment at 14.5 keV when detecting with (GeGe-)-Ge-74-Ge-76 secondary ions. The procedure allows to extract the Ge concentration profiles with good accuracy even at very high depths and at very low Ge concentrations. (C) 2004 Elsevier B.V. All rights reserved.