Optical and microstructural properties of self-assembled InAs quantum structures in silicon

The InAs quantum structures were formed in silicon by sequential ion implantation and subsequent thermal annealing. Samples were characterized by micro-Raman spectroscopy, Rutherford backscattering spectrometry (RBS), low temperature photoluminescence (PL), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). Two kinds of crystalline InAs nanostructures were successfully synthesized:quantum dots (QDs) and nanopyramides (NPs). The Raman spectrum shows two peaks at 215 and 235 cm-1 corresponding to the transverse optic (TO) and longitudinal optic (LO) InAs single-phonon modes, respectively. The narrow PL band at around 1.3 mm due to the excitation of InAs QDs with an average diameter 7.5 ± 0.5 nm was observed. The InAs NPs were found only in samples annealed for 20 ms at temperatures ranging from 1000 up to 1200 oC. The crystallinity and pyramidal shape of InAs quantum structures were confirmed by HRTEM and XRD techniques. The average size of the NPs is 50 nm base and 50 nm high and they are oriented parallel to the Si (001) planes. The lattice constant of the NPs increases from 6.051 to 6.055 Ǻ with the annealing temperature increasing from 1100 to 1200 oC due to network relaxation. Energy dispersive spectroscopy (EDS) shows almost stoichiometric composition of the InAs NPs.