Very small sized Ge dots, coherently embedded in Si, are investigated by structural and photoluminescence (PL) measurements. The Ge dot formation is induced by 0.2 monolayers (ML) of pre-deposited carbon. These carbon induced germanium (CGe)dots can be as small as 10 nm in diameter and 1 nm in height and exhibit an area density of 1 x 10(11) cm(-2). Although grown at temperatures as low as 550 degrees C a single layer of CGe islands shows intense PL signal compared to conventionally grown Ge dots grown at high temperatures. To explain the observed PL spectra we propose spatially indirect recombination of electrons confined in an underlying strain compensated Si1-x-yCxGey wetting layer and heavy holes confined in the upper Ge rich part of the island.