We fabricated single-crystalline beta -FeSi2 balls with various sizes embedded in Si crystals by reactive deposition epitaxy (RDE) and following molecular beam epitaxy (MBE). The photoluminescence (PL) depended on the size of the beta -FeSi2 ball. We observed clear 1.54 mum PL from the sample with approximately 100-nm diameter beta -FeSi2 balls, but not from the sample with the balls of approximately 150 nm in diameter or bigger. It was found from deep level transient spectroscopy (DLTS) measurements that absence of the 1.54-mum PL emission was attributed to the existence of deep levels in the Si crystals around the beta -FeSi2 balls.