L. V. Krasil’nikova

Population inversion of the energy levels of erbium ions induced by excitation transfer from the semiconductor matrix in Si-Ge based structures

Population inversion of the energy levels of Er3+ ions in Si/Si1−xGex:Er/Si (x = 0.28) structures has been achieved due to electron excitation transfer from the semiconductor matrix. An analysis of the photoluminescence kinetics at a wavelength of 1.54 μm shows that up to 80% of the Er3+ ions are converted into excited states. This effect, together with the high photoluminescence intensity observed in the structures studied, shows good prospects for obtaining lasers compatible with planar silicon technology.

Heteroepitaxy of Erbium-Doped Silicon Layers on Sapphire Substrates

The possibility of using sublimation molecular-beam epitaxy as an efficient method for growing erbium-doped silicon layers on sapphire substrates for optoelectronic applications is analyzed. The advantage of this method is that the erbium-doped silicon layers can be grown at relatively low temperatures. The use of sublimation molecular-beam epitaxy makes it possible to grow silicon layers of good crystal quality. It is demonstrated that the growth temperature affects not only the structure of silicon-on-sapphire layers but also the crystallographic orientation of these layers. The electrical and luminescence properties of the erbium-doped silicon layers are discussed. It is revealed that structures of this type exhibit intense erbium photoluminescence at a wavelength of 1.54 μm.

Structural and photoluminescence properties of heteroepitaxial silicon-on-sapphire layers

The growth of erbium-doped silicon layers on sapphire substrates through sublimation molecular-beam epitaxy is studied for the first time. Structural analysis data are given, and the luminescence properties of layers are discussed. Heteroepitaxial silicon-on-sapphire layers grown at a temperature Ts=600–700°C are found to be fairly perfect in structure. Photoluminescence spectra show a peak at a wavelength of 1.54 µm associated with intracenter transitions in the rare earth Er3+ ion.

Model of photoluminescence from ion-synthesized silicon nanocrystal arrays embedded in a silicon dioxide matrix

A four-level model of photoluminescence from Si nanocrystal arrays embedded in a SiO2 matrix is suggested. The model allows for thermally activated transitions between singlet and triplet levels in the exchange-split energy state of an exciton in an excited silicon nanocrystal. An expression is derived for the temperature dependence of the intensity of photoluminescence monochromatic components. A correlation is found between the amount of splitting and the emitted photon energy by comparing model data with our experimental data for ion-synthesized Si nanocrystals in a SiO2 matrix. The model explains the finiteness of the photoluminescence intensity at temperatures close to 0 K and the nonmonotonicity of the temperature run of the intensity.

Analysis of the gain and luminescence properties of Si/Si1−xGx: Er/Si heterostructures produced by sublimation molecular-beam epitaxy in a gas phase

Si/Si1−xGex: Er/Si structures grown by sublimation molecular-beam epitaxy (SMBE) in a gas phase are studied. These structures are considered possible structures for realizing a Si/Er-based laser. It is shown that SMBE in a gas phase can be applied to create effective light-emitting structures that generate an intense luminescence signal at a wavelength of 1.54 μm. The structures and chemical compositions of the Si/Si1−xGx: Er/Si structures, whose parameters are close to those calculated for creating laser-type structures, are examined, and their photoluminescence (PL) spectra and kinetics are studied at 4.2 and 77 K. It is shown that the fraction of Er3+ optically active centers in the Si1−xGx: Er layers thus grown reaches ∼10% of the total erbium-impurity concentration. The optical gains in the active Si1−xGx: Er layers at x = 0.1 and 0.02 are estimated to be ∼0.03 and ∼0.2 cm−1, respectively. The gain in structures of this type can be significantly increased via the intentional formation of isolated Er3+ optically active centers whose PL spectra have a characteristic fine structure.

Specific features of the photoexcitation spectra of epitaxial InN layers grown by molecular-beam epitaxy with the plasma activation of nitrogen

The results of studies of the photoexcitation spectra of epitaxial InN layers formed by molecular-beam epitaxy with the plasma activation of nitrogen are reported. The concentration of free charge carriers in the layers is 1018–1019 cm–3. The photoconductivity, photoluminescence, and absorption spectra exhibit a shift of the long-wavelength threshold of interband transitions in accordance with the Burstein–Moss effect for n-InN with different concentrations of equilibrium electrons. In the samples, absolute negative photoconductivity with a nanosecond relaxation time is observed. The results of photoelectric, absorption, and luminescence spectroscopy experiments are correlated with the technological parameters and electron microscopy data.

Absorption cross section for the 4I15/2 → 4I13/2 transition of Er3+ in Si:Er:O/SOI epitaxial layers

Optical losses caused by the interaction of radiation with optically active Er3+ ions in epitaxial waveguide structures Si:Er/SOI have been directly measured. The cross section for the 4I13/2 → 4I15/2 radiative transition in the Er3+ ion has been estimated as σ300 K ∼ 8 × 10−19 cm2 at T = 300 K and σ10 K ∼ 10−17 cm2 at T = 10 K.

Si/Si1 − x Ge x : Er/Si(100) heterostructures grown by sublimation of silicon in germane gas atmosphere

High-quality Si1 − xGex:Er epitaxial layers have been grown on Si(100) substrates at a relatively low temperature (500°C) by sublimation of silicon in GeH4 gas atmosphere. It has been established using capacitance-voltage measurements, X-ray diffraction, and secondary-ion mass spectrometry that the spread in the deposited layer thickness in the central part of the substrate (40 × 10 mm2 in size) is 5%. High homogeneity of layer doping is obtained within the same area.

Effect of the p-n junction breakdown mechanism on the Er3+ ion electroluminescence intensity and excitation efficiency in Si: Er epitaxial layers grown through sublimation molecular beam epitaxy

A series of Si: Er/Si light-emitting diode structures with a smoothly varying p-n junction breakdown mechanism, grown through sublimation molecular-beam epitaxy, is used to investigate the effect of the breakdown mechanism on the electroluminescence of the structures. The maximal intensity and excitation efficiency of room-temperature Er3+ ion electroluminescence are shown to be attained in diode structures with a mixed breakdown mechanism.