We report the ability to arrange self-organized Ge islands on patterned Si ͑001͒ substrates. Selective epitaxial growth of Si is carried out with gas-source molecular beam epitaxy to form Si mesas followed by subsequent Ge growth. Self-aligned and regularly spaced Ge islands are formed on the ͗110͘-oriented ridges of the Si stripe mesas. A mono-modal size distribution of the islands has been observed on the ridges. Using preferential nucleation sites allows us to place Ge islands at predetermined positions. The controlled arrangement of self-organized nanostructures offers the potential applications of island arrays for the implementation in nanoelectronics and quantum computation.

Recently proposed thermoelectric applications of quantum dot superlattices made of different material systems depend crucially on the values of the electrical and thermal conductivities in these nanostructures. We report results of the measurements of Hall mobility and thermal conductivity in a set of Ge 0.5 Si 0.5 /Si quantum dot superlattices. The average measured in-plane Hall mobility for the undoped Ge/Si quantum dot superlattices on a p-type substrate is 233.5 cm 2 V −1 s −1 at room temperature and 6.80 ϫ 10 3 cm 2 V −1 s −1 at 77 K. The average value of the thermal conductivity measured by 3 method is about 10 W/mK at room temperature and 3.5 W/mK at 77 K. In the low-temperature region, the thermal conductivity is proportional to T 0.7 − T 0.9 . Relatively large values of the carrier mobility and its temperature dependence suggest that the carrier transport in the investigated structures is likely of the band conduction type rather than hopping type. The thermal conductivity of the Ge 0.5 Si 0.5 /Si quantum dot superlattices is strongly reduced and has its peak value shifted toward the high temperatures as compared to the constituent bulk materials. Obtained results can be used for Ge x Si 1−x /Si quantum dot superlattice structure optimization for the high-temperature thermoelectric applications.

A triangleshaped nanoscale metal-oxide-semiconductor device