Structural Analysis of Si-Based Nanodot Arrays Self-Organized by Selective Etching of SiGe/Si Films

Abstract

Atomic force microscopy (AFM) revealed the surface structures of nanodot arrays fabricated by selective etching of SiGe/Si films that have pure-edge dislocation networks at the SiGe–Si interface. By varying the etching time, it is possible to control the composition of the nanodot arrays, allowing either SiGe or Si nanodot arrays to be fabricated. The surface roughness of the nanodot arrays does not originate from the nanodots themselves, but from the spatial variation in the depth of dislocations in the SiGe/Si films prior to etching. Individual nanodots in SiGe nanodot arrays have smoother profiles than those in Si nanodots although the nanodots in SiGe and Si nanodot arrays have similar heights and diameters. The rougher surface of individual Si nanodots is due to the lower etching selectivity, which results from the smaller dislocation influence on the etching reaction in Si substrates far from the interface. Transmission electron microscopy images reveal the formation of arrays of epitaxial SiGe nanodots with smooth surfaces, which is consistent with the AFM results.