Effect of growth conditions on photoluminescence of erbium-doped silicon layers grown using sublimation molecular-beam epitaxy

Erbium-doped epitaxial silicon layers were grown using two different growth techniques, namely, commonly used molecular-beam epitaxy (MBE) and solid-phase epitaxy (SPE). It is shown that an erbium-doped silicon epitaxial layer deposited through SPE on a cold substrate and subsequently annealed displays amore intense photoluminescence at a wavelength of 1.54 μm than do MBE-grown layers. __________ Translated from Fizika Tverdogo Tela, Vol. 46, No. 1, 2004, pp. 102–104. Original Russian Text Copyright ? 2004 by Shengurov, Svetlov, Chalkov, Andreev, Krasil’nik, Kryzhkov.     

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 T _s=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. __________ Translated from Fizika Tverdogo Tela, Vol. 46, No. 1, 2004, pp. 15–17. Original Russian Text Copyright ? 2004 by Svetlov, Chalkov, Shengurov, Drozdov, Krasil’nik, Krasil’nikova, Stepikhova, Pavlov, Pavlova, Shilyaev, Khokhlov. Deceased.     

Crystal lattice defects and Hall mobility of electrons in Si: Er/Si layers grown by sublimation molecular-beam epitaxy

The density of crystal lattice defects in Si: Er layers grown through sublimation molecular-beam epitaxy at temperatures ranging from 520 to 580°C is investigated by a metallographic method, and the Hall mobility of electrons in these layers is determined. It is found that the introduction of erbium at a concentration of up to ～5 × 10¹⁸ cm^?3 into silicon layers is not accompanied by an increase in the density of crystal lattice defects but leads to a considerable decrease in the electron mobility.     

Thickness uniformity of silicon layers grown from a sublimation source by molecular-beam epitaxy

The thickness distributions of epitaxial layers over the substrate area are experimentally and theoretically studied for deposition from a molecular beam formed by a sublimation source in vacuum. The calculated data agree well with the experimental results for the molecular-beam epitaxy of silicon.     

Luminescent properties of MBE-grown Si:Er/SOI structures

Here we report on luminescent properties of multilayer Si:Er structures grown by sublimation molecular-beam epitaxy on “silicon-on-insulator” substrates. We demonstrate formation in such structures of a unique erbium-related center Er-1. This optical complex stands out among other known erbium-related centers in silicon for its record narrow luminescent line (<10 μeV) and largest absorption cross-section and, therefore, provides the best conditions to achieve practically significant amplification and stimulated emission in erbium-doped silicon structures.     

Elemental composition of nanoclusters formed by pulsed irradiation with low-energy ions during Ge/Si epitaxy

Multilayer silicon structures with built-in layers of Ge nanoclusters were studied experimentally by Raman light scattering. The built-in layers were formed by the pulsed action of a low-energy beam of intrinsic ions during molecular-beam epitaxy. It is found that the ion-stimulated nucleation and the subsequent growth make it possible to obtain Ge nanoclusters almost free of Si.     

Self-organization of germanium nanoislands obtained in silicon by molecular-beam epitaxy

Nanometer germanium islands in epitaxial layers of silicon are obtained by molecular-beam epitaxy. The dimensions and shapes of the islands are determined in an atomic-force microscope. The photoluminescence spectra are found to contain lines that can be interpreted as quasidirect optical transitions in the islands. It is concluded on the basis of optical and microprobe measurements and theoretical calculations of the energies of electronic states that silicon is dissolved in the germanium islands. Values of the germanium and silicon contents in the solid solution are presented. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 1, 46–50 (10 January 1998)     

Comparison of organic thin films deposited by supersonic molecular-beam epitaxy and organic molecular-beam epitaxy: The case of titanyl phthalocyanine

Recently, supersonic molecular-beam epitaxy (SuMBE) was invented as an alternative method for the deposition of organic material, using higher kinetic energies for deposition than conventional organic molecular-beam epitaxy (OMBE). Using titanyl phthalocyanine (TiOPc) as a model substance, we show that the SuMBE deposition results in increased crystal quality of the deposited material. This is induced by the high kinetic energy of the molecular-beam in SuMBE, which leads to increased molecular mobility on the surface, resulting in larger crystal sizes and higher crystal quality. Alternatively, similar films as made by OMBE can be deposited by SuMBE at lower substrate temperatures. This temperature reduction may be of interest for the deposition of stacked organic devices on underlying heat sensitive layers, as they are quite common in organic electronic devices.     

Morphology and photoluminescence of self-assembled GeSi/Si nanoclusters grown by sublimation molecular-beam epitaxy in a GeH<Subscript>4</Subscript> ambient

The dependence of the morphology and photoluminescence spectra of GeSi/Si(001) heterostructures with self-assembled nanoclusters, obtained by sublimation molecular-beam epitaxy in a GeH₄ ambient, on the growth conditions has been analyzed. The conditions for obtaining structures with uniform nanocluster arrays exhibiting photoluminescence at room temperature have been determined.     

Silicon–Platinum Silicide Schottky Barriers with a Highly-Doped Surface Layer

The spectral characteristic of infrared silicon–platinum silicide Schottky barrier photodetectors is shifted to the long wavelength region due to a highly-doped surface silicon layer produced by recoil boron implantation. The dependence of the resulting highly-doped layer parameters on high-energy boron-ion implantation regimes is studied experimentally. Energy-band diagrams and reduction of the barrier height are calculated for p-Si–PtSi structures with highly-doped surface layers produced by molecular-beam epitaxy and recoil implantation.     

Light-emitting Si: Er structures prepared by molecular-beam epitaxy: Structural defects

The structural defects in silicon layers grown by molecular-beam epitaxy and doped with erbium up to concentrations [Er] = 4 × 10¹⁹ cm^?3 are studied using transmission electron microscopy and high-resolution electron microscopy. It is established that the main types of extended structural defects at erbium concentrations [Er] ≥ 2 × 10¹⁹ cm^?3 are 4-to 25-nm Er spherical precipitates located at the “epitaxial layer-substrate” boundary and platelike ErSi₂ precipitates residing in the { 111} planes throughout the thickness of the layer.     

Photoelectric properties and electroluminescence of <Emphasis Type="Italic">p-i-n</Emphasis> diodes based on GeSi/Si heterostructures with self-assembled nanoclusters

This paper reports on the results of investigations into the photoelectric properties and electroluminescence of p-i-n diodes based on GeSi/Si heterostructures with GeSi self-assembled nanoclusters embedded in the i region. The p-i-n diodes are grown through sublimation molecular-beam epitaxy using a vapor-phase source of germanium. The photovoltage spectra of the p-i-n diodes measured at a temperature of 300 K exhibit a photosensitivity band attributed to interband optical transitions in the GeSi nanoclusters. A new approach to analyzing the photosensitivity spectra of the heterostructures containing GeSi thin layers is proposed, and the energy at the edge of the photosensitivity bands assigned to these layers is determined. The electroluminescence observed in the p-i-n diodes at 77 K is associated with the radiative interband optical transitions in GeSi nanoclusters.     

Mechanism of silicon epitaxy on porous silicon layers

The mechanism of silicon epitaxy on porous Si(111) layers is investigated by the Monte Carlo method. The Gilmer model of adatom diffusion extended to the case of arbitrary surface morphology is used. Vacancies and pendants of atoms are allowed in the generalized model, the activation energy of a diffusion hop depends on the state of the neighboring positions in the first and second coordination spheres, and neighbors located outside the growing elementary layer are also taken into account. It is shown that in this model epitaxy occurs by the formation of metastable nucleation centers at the edges of pores, followed by growth of the nucleation centers along the perimeter and the formation of a thin, continuous pendant layer. Three-dimensional images of surface layers at different stages of epitaxy were obtained. The dependence of the kinetics of the epitaxy process on the amount of deposited silicon is determined for different substrate porosities. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 7, 512–517 (10 April 1998)     

Morphological transformation of a germanium layer grown on a silicon surface by molecular-beam epitaxy at low temperatures

Multilayer Si/Ge nanostructures with germanium layers of different thicknesses are grown by molecular-beam epitaxy at low temperatures (<350°C) and studied using photoluminescence and atomic force microscopy. It is found that the germanium layer undergoes a morphological transformation when its thickness becomes equal to approximately five monolayers: an island relief transforms into a smooth undulating relief.     

Mechanisms of dislocation generation in Si structures with strained layers: Intrinsic point defects in dislocation nucleation

The peculiarities of dislocation production in silicon compositions with elastically strained layers fabricated by the molecular-beam epitaxy technique (SiGe/Si heterostructures) and by direct bonding of Si(110)/Si(100) wafers are studied with transmission electron microscopy. The role of intrinsic point defects during the process of nucleation of misfit dislocations is explained. The surplus concentration of these defects in heterostructures was produced via low-temperature epitaxial growth of buffer layers or with ion implantation of elastically strained heterostructures. The model of “optimal” and “inverse” intrinsic point defects providing an explanation for the relaxation of misfit strains in heterostructures is proposed.     

Effects of spatial ordering of quantum dot arrays from small-angle X-ray diffraction data under variation of growth parameters

The small angle X-ray diffraction method is applied to the system of germanium quantum dots in the silicon matrix prepared by molecular-beam epitaxy in self-organization mode using the Stranski-Krastanov technique. Depending on the growth mode, the specific distances between Ge quantum dots and deviations from their correlated distribution are determined. The results are in agreement with the scanning tunneling microscopy data.     

Photoelectric Properties of Photodetectors Based on Silicon–Platinum Silicide Schottky Barriers with a Highly-Doped Surface Layer

We have calculated the spectral, threshold, and noise characteristics of p-Si–PtSi photodetectors with highly-doped surface layers produced by molecular-beam epitaxy and short-pulse ion implantation by a recoil method.     

Simulation of porous silicon formation and silicon epitaxy on its surface

Processes of porous silicon formation and silicon epitaxy on its surface are studied using the Monte Carlo method. The model for porous silicon formation under anode etching allows for non-uniformity of charge distribution over the silicon-electrolyte interface. Processes of diffusion, generation and recombination of holes, as well as dimensional quantization, are also considered. Gilmer's model, extended to the case of a rough surface, is used to study epitaxy. The structures obtained by simulations at different levels of doping of the crystal substrate and for various parameters (temperature, HF concentration, and anode current density) are presented. Analysis of nanoporous structures showed that the porosity changes with depth, and fractal dimensionality exists below 10 nm. It has been shown that epitaxy, developing by formation of metastable nuclei at the edges of pores, by their subsequent growth along the perimenter and by formation of a thin continuous overhanging layer, may be described within the framework of this model. Three-dimensional images of near-surface layers formed at different stages of epitaxy have been obtained. The dependence of the epitaxy kinetics on the amount of deposited silicon for different structure porosities has been revealed. Institute of Physics of Semiconductors, Siberian Branch, Russian Academy of Science. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 49–56, March, 1999.     

Effect of the <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">n</Emphasis> junction breakdown mechanism on the Er<Superscript>3+</Superscript> 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.     

AlGaN/GaN heterostructure study using Rutherford backscattering spectrometry

Rutherford backscattering spectroscopy (RBS) was used to study the structural peculiarities and the presence of the background impurities in AlGaN/GaN heterostructures grown on substrates from different materials (α-Al₂O₃, SiC, and Si) by means of gas-phase epitaxy from the metal-organic compounds and molecular-beam epitaxy. Redistribution of the elements in the working layers of these heterostructures during formation of the ohmic contacts was analyzed. These studies confirmed the informativity of the applied method for revealing the peculiarities of stoichiometry of heterostructures with submicron and nanoscale layers. Oxygen was found to be a background impurity in heterostructures grown on sapphire substrates. It was not detected, however, in heterostructures grown on substrates of other materials. Intermixing of the working layers of heterostructures was observed in the process of the Ohmic contact formation. The local intermetallic phases of compounds of the sputtered metals in the selected modes were revealed after annealing at T = 650–700°C.