Ge quantum dots (QDs), incorporated in thin SiO₂ layers, are of great interest for both fundamental and application reasons. Ge QDs were successfully employed in Flash memory devices, optoelectronic gadgets, single-electron transistors etc. It has been recently demonstrated that ion-implantation is a gentle instrument for further modification of SiO₂+Ge-QDs structure, synthesis of Ge-nanoclusters and SiO₂/Ge nanosrtructures, ion-driven self-organization of two-dimensional layers of Ge QDs and might be used for modification of opto-electrical properties of MOS. Specifically, doping of Ge QDs with phosphorus and boron results in enhancement of the luminescence yield in LEDs and increasing of flat-band voltage shift in memory devices.

In this talk we present recent results of structural and electrical investigations of SiO₂ layers with incorporated Ge QDs. Thin layers of SiGe alloy were first deposited by CVD on (001)-Si substrate covered with thermally grown SiO₂ layer. Phosphorus or boron ions were then implanted at 100 keV to fluency of 10¹³ – 10¹⁵ cm^-2. High temperature thermal oxidation and annealing were finally carried out. The structures were investigated by TEM in plan-view and cross-section geometries with a Philips CM20 instrument. The composition of the layers was tested by RBS. MOS mesa-structures were finally prepared and high-frequency C-V and I-V measurements were done.

It is found that ion implantation results in modification of both structural and electrical properties of Ge quantum dots incorporated in SiO₂ layers. The effects of implantation damage, impurity type and thermal treatment conditions on flat band voltage shift and leakage current of MOS structures are observed. The results are discussed in terms of ion-beam doping and radiation defect formation.