The intra-4f transition close to 1.54 μm of Er implanted into Si shows rich fine structure due to the crystal field of different defect types. Making use of the influence of implantation and annealing parameters, additional doping, temperature, and excitation power, we identify groups of lines belonging to different Er-related, optically active defects: the isolated interstitial Er, axial symmetry Er complexes with oxygen, and Er complex centers containing residual radiation defects. We show that the exciton binding energies as well as nonradiative quenching rates differ for different Er centers. Under optimum annealing conditions, the isolated interstitial Er has the highest photoluminescence yield at temperatures above 100 K. © 1996 The American Physical Society.

The dielectric function of nanocrystalline silicon (nc-Si) with crystallite size in the range of 1 to 3 nm has been determined by spectroscopic ellipsometry in the range of 1.5 to 5.5 eV. A Tauc–Lorentz parameterization is used to model the nc-Si optical properties. The nc-Si dielectric function can be used to analyze nondestructively nc-Si thin films where nanocrystallites cannot be detected by x-ray diffraction and Raman spectroscopy.

We report direct excitation of optically active Er centers in porous Si. Excitation spectroscopy performed close to the intracenter I415/2→I411/2 and I415/2→I49/2 transitions of Er3+ (4f11) ions allows us to identify two kinds of Er centers in porous Si: (i) Er diffused into porous nanograins with lower than cubic symmetry and (ii) Er centers incorporated in an amorphous silicalike matrix. The latter show much weaker thermal quenching of the Er3+ emission which decreases only by a factor of eight when the temperature is increased from 4.2 K up to 360 K.

Luminescent properties of self-assembled Ge(Si)/SOI nanoislands embedded in two-dimensional photonic crystal (PhC) slabs with and without L3 cavities were studied with PhC period a varied between 350 and 600 nm. For small periods ( a ≤ 450 nm), the nanoisland luminescence, which spans over the wavelength range from 1.2 to 1.6 μ m, overlaps with the PhC bandgap resulting in a coupling with the localized modes of an L3 cavity. It is shown that for larger periods ( a > 450 nm), nanoisland emission couples to the radiative modes above the bandgap located in the vicinity of the Г-point of the photonic crystal Brillouin zone and is characterized by the low group velocity. In this case, a significant (up to 35-fold) increase in the PL intensity was observed in a number of PhCs without a cavity. From a technological point of view, the latter result makes such types of photonic crystal structures particularly promising for the realization of Si-based light emitters operating in the telecommunication wavelength range because, firstly, their manufacture does not require a precise cavity formation and, secondly, they provide a much larger area for the radiating region, as compared with PhC cavities.