Nanometer-scale Al particles are fabricated and are embedded in a GaAs matrix using molecular beam epitaxial technique. The Al particle is self-assembled on GaAs by supplying an Al molecular beam. The average particle size is found to be 25 nm. The density is 7 x 10(10) cm(-2) when Al of 6.2 x 10(15) atoms/cm(2) is supplied on (1 0 0)GaAs at a substrate temperature of 300 degrees C. Clear hysteresis and plateaus in capacitance-voltage (C-V) curves are found in an Al-embedded sample, whereas monotonic increase of capacitance is obtained in a reference sample having an AlAs layer instead of Al. This difference results from trapping of electrons by the Al particles, suggesting that the particles have metallic character. (c) 2006 Elsevier B.V. All rights reserved.