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Controlled doping with an effective carrier concentration higher than 10^20 cm-3 is a key challenge for the full integration of Ge into silicon-based technology. Such a highly doped layer of both p- and n type is needed to provide ohmic contacts with low specific resistance. We have studied the effect of ion implantation parameters i.e., ion energy, fluence, ion type, and protective layer on the effective concentration of electrons. We have shown that the maximum electron concentration increases as the thickness of the doping layer decreases. The degradation of the implanted Ge surface can be minimized by performing ion implantation at temperatures that are below -100 C with ion flux less than 60 nAcm-2 and maximum ion energy less than 120 keV. The implanted layers are flash-lamp annealed for 20 ms in order to inhibit the diffusion of the implanted ions during the recrystallization process.

Ge with a quasi-direct band gap can be realized by strain engineering, alloying with Sn, or ultrahigh n-type doping. In this work, we use all three approaches together to fabricate direct-band-gap Ge−Sn alloys. The heavily doped n-type Ge−Sn is realized with CMOS-compatible nonequilibrium material processing. P is used to form highly doped n-type Ge−Sn layers and to modify the lattice parameter of P-doped Ge−Sn alloys. The strain engineering in heavily-P-doped Ge−Sn films is confirmed by x-ray diffraction and micro Raman spectroscopy. The change of the band gap in P-doped Ge−Sn alloy as a function of P concentration is theoretically predicted by density functional theory and experimentally verified by near-infrared spectroscopic ellipsometry. According to the shift of the absorption edge, it is shown that for an electron concentration greater than 1 × 10^20 cm the band-gap renormalization is partially compensated by the Burstein-Moss effect. These results indicate that Ge-based materials have high potential for use in near-infrared optoelectronic devices, fully compatible with CMOS technology.

Ge with a quasi-direct band gap can be realized by strain engineering, alloying with Sn, or ultrahigh n-type doping. In this work, we use all three approaches together to fabricate direct-band-gap Ge−Sn alloys. The heavily doped n-type Ge−Sn is realized with CMOS-compatible nonequilibrium material processing. P is used to form highly doped n-type Ge−Sn layers and to modify the lattice parameter of P-doped Ge−Sn alloys. The strain engineering in heavily-P-doped Ge−Sn films is confirmed by x-ray diffraction and micro Raman spectroscopy. The change of the band gap in P-doped Ge−Sn alloy as a function of P concentration is theoretically predicted by density functional theory and experimentally verified by near-infrared spectroscopic ellipsometry. According to the shift of the absorption edge, it is shown that for an electron concentration greater than 1 × 10^20 cm the band-gap renormalization is partially compensated by the Burstein-Moss effect. These results indicate that Ge-based materials have high potential for use in near-infrared optoelectronic devices, fully compatible with CMOS technology.

The In(As, N) quantum structures were formed in silicon, SiO2 and Si3N4 films by sequential ion implantation and subsequent thermal annealing. Samples were characterized by -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 optical (TO) and longitudinal optical (LO) InAs phonon modes, respectively. The narrow PL band at around 1.3 m from the 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 temperature range from 1000 up to 1200 oC. The crystallinity and pyramidal shape of InAs quantum structures were confirmed by high resolution transmission electron microscopy (HRTEM) (see Fig. 1) and X-ray diffraction (XRD). 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 InAs nanopyramids grow in silicon due to liquid phase epitaxy. The InN crystals are formed on the top of silicon nitride layer due to outdiffusion of indium and in Si3N4 film. The PL measurements shows narrow band at around 1.35 m originated from hexagonal InN nanocrystals due to quantum confinement size effect. -Raman scattering study shows two peaks at 495 and 588 cm-1, which correspond to (TO) of E2h and (LO) of A1 phonon modes, respectively.

The In(As, N) quantum structures were formed in silicon, SiO2 and Si3N4 films by sequential ion implantation and subsequent thermal annealing. Samples were characterized by -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 optical (TO) and longitudinal optical (LO) InAs phonon modes, respectively. The narrow PL band at around 1.3 m from the 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 temperature range from 1000 up to 1200 oC. The crystallinity and pyramidal shape of InAs quantum structures were confirmed by high resolution transmission electron microscopy (HRTEM) (see Fig. 1) and X-ray diffraction (XRD). 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 InAs nanopyramids grow in silicon due to liquid phase epitaxy. The InN crystals are formed on the top of silicon nitride layer due to outdiffusion of indium and in Si3N4 film. The PL measurements shows narrow band at around 1.35 m originated from hexagonal InN nanocrystals due to quantum confinement size effect. -Raman scattering study shows two peaks at 495 and 588 cm-1, which correspond to (TO) of E2h and (LO) of A1 phonon modes, respectively.