Structural and optical properties of Ge nanocrystals in SiO/sub 2/ glasses fabricated by multi-energy ion implantation

The discovery of efficient photoluminescence (PL) from Si and Ge nanocrystals at room temperature has stimulated considerable efforts in understanding optical properties of indirect-gap group IV semiconductor nanocrystals. Bulk Ge crystal has a larger dielectric constant and smaller effective masses of carriers compared to the case of bulk Si crystal. Then, it is expected that quantum confinement effects would appear more pronounced in Ge nanocrystals than in Si nanocrystals. Recently, a number of different techniques have been developed to synthesize semiconductor nanocrystals. In particular, high-dose ion implantation is one of the most versatile techniques for nanocrystal fabrication, because the nanocrystal size can be controlled by changing the ion dose, the kinetic energy of ions and the annealing temperature. In this work, we have fabricated light-emitting Ge nanocrystals by means of Ge/sup +/ ion implantation into SiO/sub 2/ glasses followed by thermal annealing. Using multi-energy ion implantation techniques, the Ge nanocrystals samples with very small size fluctuation are obtained and these samples show near-infrared PL with a narrow spectral bandwidth.