Bimodal distribution of Ge islands on Si(001) grown by LPCVD

Hut- and dome-shaped islands have been observed during low-pressure vapour phase epitaxy (LPVPE) of Ge on Si(001) at 700°C. The experiments show an island height increase with increasing deposition time (total Ge-coverage was kept constant). The shape transition from huts to domes, which takes place after hut clusters have reached a baselength of 90 nm, indicates that huts are not a stable configuration. The two different island types are found to be the reason for the bimodal nature of the size distribution. Photoluminescence measurements show a linear correlation between hut cluster density and integrated photoluminescence intensity.