Growth temperature dependence on the formation of carbon-induced Ge quantum dots

Abstract

Carbon has been exploited to form Ge quantum dots since it can provide effective nucleation sites. In this study, C-induced Ge quantum dots grown by solid source molecular beam epitaxy are investigated as a function of pre-deposited C coverage, overgrown Ge coverage, and substrate temperature using atomic force microscopy. The smallest quantum dots with a 300 Å mean lateral diameter, a 50 Å mean height, and an areal density of 3.0×1010 cm−2 are obtained with 0.1 monolayer C pre-deposition and a 3 monolayer thick Ge overlayer. Growth temperature dependence for the Ge dot growth reveals that the dot density and size are abruptly changed by two orders of magnitude near 500°C. This is attributed to the difference in the temperature-dependent surface diffusivities of Ge and C adatoms on Si(100) substrate. The experimental results suggest that growth temperature plays a key role and should be kept below 500°C.