Su/beta-FeSi2 film/Si double-heterostructures (DH) were fabricated by molecular beam epitaxy (MBE) on Si(111) substrates. Influence of annealing temperature on the structure of beta-FeSi2 embedded in Si and electroluminescence (EL) intensity was investigated. In the case that the annealing temperature was 800 degrees C, the beta-FeSi2 remained as a continuous film in the DH regardless of its thickness. In contrast, a 90-nm-thick beta-FeSi2 film agglomerated into islands in the DH after annealing at 900 degrees C, but agglomeration was prevented for thicker beta-FeSi2 (250 nm). The EL intensity of beta-FeSi2 measured at 77 K was significantly enhanced by annealing at 900 degrees C compared to that at 800 degrees C. This improvement is considered to be due to the reduction in the number of nonradiative recombination centers in the beta-FeSi2 films. (c) 2005 Elsevier B.V. All rights reserved.