Growth dynamics of C-induced Ge dots on Si1−xGex strained layers

We address the growth mechanism of Ge quantum dots (QDs) on C-alloyed strained Si1−xGex layers by in situ reflection high-energy electron-diffraction (RHEED). We show that C-induced growth on a Si-rich surface leads to a high density (about 1011 cm−2) of small dome-shaped islands. On surfaces up to ≈65% richer in Ge we observe a decrease of the dot density by two orders of magnitude, which is associated to the increase of the adatom diffusion. Based on quantitative RHEED analysis, the islands are believed to grow in a Volmer-Weber mode even though their spotty electron transmission pattern is not detectable in the initial stages of growth due to the reduced size of the three-dimensional nucleation islands.