ANNEALING EFFECTS ON CARBON-INDUCED GERMANIUM DOTS IN SILICON

The growth of 2.4 monolayers Ge on 0.2 monolayers of predeposited C on Si results in the formation of 15 nm size Ge islands. Fifty stacked l ayers of these C-induced Ge dots are grown on Si (001) at 460 degrees C. Different pieces of the wafer an annealed at temperatures between 4 60 and 950 degrees C and for times ranging from 1 to 20 min at 850 deg rees C. For temperatures higher than 550 degrees C, a pronounced energ y blueshift and an evolution from one broad photoluminescence peak to two well-resolved lines reflect a gradual transition from quantum dot states to quantum well-like states. As transmission electron microscop y images illustrate, diffusion processes completely smear out the shar p interfaces between the dots and the surrounding Si. An activation en ergy of only 1.6 eV and temperature-dependent diffusion coefficients a re derived from simple model calculations. (C) 1998 American Institute of Physics. [S0003-6951(98)04025-X].