The Formation of Narrow Nanocluster Bands in Ge-Implanted SiO₂-Layers

The paper describes the formation of Ge nanocrystals in thin thermally grown SiO₂ layers (d_ox=<100 nm) using implantation of 10¹⁵ - 2x10¹⁶ Ge⁺/cm² and subsequent annealing. Although the implanted Ge depth profile is distributed over almost the whole SiO₂ layer, a very narrow band (typical width 5 nm) of Ge nanoclusters very close but well-separated to the Si/SiO₂-interface is formed by self-organization under specified annealing conditions. A possible mechanism for this self-organization process is discussed including nucleation phenomena, Ostwald ripening and defect-stimulated interface processes. Simple MOS-structures were prepared and the effect of charge storage inside the clusters has been derived from C-V characteristics.