FORMATION OF CARBON-INDUCED GERMANIUM DOTS

A very small amount of pre-deposited C on a Si substrate causes island formation after epitaxial growth of less than 2 monolayers Ge. These C-induced Ge dots can be as small as 10 nm in lateral size and 1 nm in height. Their areal density is 10(11) cm(-2). Intense photoluminescen ce signal from these small Ge quantum dots is observed reaching a maxi mum for 2.1+/-0.3 monolayers of Ge. In the initial stages of island fo rmation, the optical transition of the wetting layer is blue-shifted b y strain compensation effects. We propose spatially indirect mechanism s of radiative recombination between electrons confined in the underly ing wetting layer and holes confined in the Ge islands. (C) 1997 Ameri can Institute of Physics.