INFLUENCE OF PRE-GROWN CARBON ON THE FORMATION OF GERMANIUM DOTS

Very small sized Ge dots, coherently embedded in Si, are investigated by structural and photoluminescence (PL) measurements. The Ge dot form ation 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 diamet er 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 laye r of CGe islands shows intense PL signal compared to conventionally gr own Ge dots grown at high temperatures. To explain the observed PL spe ctra we propose spatially indirect recombination of electrons confined in an underlying strain compensated Si1-x-yCxGey wetting layer and he avy holes confined in the upper Ge rich part of the island. (C) 1998 E lsevier Science S.A. All rights reserved.