We demonstrate that ultralow-level Al impurities on a silicon surface can be measured by using the high-resolution grazing emission x-ray fluorescence (GEXRF) technique combined with synchrotron-radiation excitation. An Al-impurity level of about 1012 atoms/cm2 was reached by observing the Al Kα x-ray fluorescence in the resonant Raman-scattering background-“free” regime by choosing an appropriate beam energy below the Si K absorption edge. Present results show that by combining the GEXRF method with the vapor phase decomposition technique the 107 atoms/cm2 level can be reached for Al detection on silicon. Finally, we found that the high-resolution GEXRF technique is a sensitive tool to study the morphology of surface nanostructures.