Silicon LEDs with room-temperature dislocation-related luminescence, fabricated by erbium ion implantation and chemical-vapor deposition of polycrystalline silicon layers heavily doped with boron and phosphorus

Light-emitting diodes (LEDs) have been fabricated in which optically active centers are formed by implantation of erbium ions into silicon and subsequent high-temperature annealing in an oxidizing atmosphere and the p-n junction and the ohmic contact are formed by chemical vapor deposition of polycrystalline silicon layers doped with boron and phosphorus, respectively. The luminescent properties of the LEDs have been studied. Use of polycrystalline layers makes it possible to eliminate the losses in the bulk of the light-emitting Si:Er layer. These losses are inevitable if the conventional ion implantation and diffusion methods are employed. At 80 K, the variation of electroluminescence spectra in the spectral range of the dislocation-related luminescence with the drive current is well described if the spectrum is decomposed into three Gaussian components whose peak positions and widths are current-independent and amplitudes linearly increase with the current. At 300 K, a single peak is observed in the spectral range of the dislocation-related luminescence at ～1.6 μm.     

EBIC study of nonradiative recombination in silicon LEDs with near-band-edge luminescence

Silicon light-emitting diode structures with a near-band-edge luminescence have been studied by the EBIC method. The structures were fabricated by ion implantation with different temperatures of the final stage of the postimplantation annealing (950 and 1000°C). Upon raising the annealing temperature, the diffusion length of minority carriers increases from 1–2 to 25–35 μm in the light-emitting diode region in which the near-band-edge luminescence occurs. Also, the distribution of nonradiative recombination centers in this region becomes less nonuniform in the lateral direction, parallel to the plane of the p-n junction. It is these factors that lead to the observed substantial increase in the intensity of the near-band-edge luminescence.     

Influence of intrinsic point defects on the formation of structural defects and optically active centers during the annealing of erbium-and dysprosium-implanted silicon

The photoluminescence spectra and behavior of the structural defects in layers obtained by implanting 1.0–1.8-MeV Er and Dy ions at a dose of 1×10¹³ cm⁻² are investigated after annealing at 1000–1200 °C for 0.5–1 h in argon or a chlorine-containing atmosphere. The structural defects are studied using transmission electron microscopy and selective chemical etching. The dominant features in the luminescence spectra of the Si:Er and Si:Dy layers following annealing in the chlorine-containing atmosphere are lines associated with the formation of edge dislocations, while the dominant features following the annealing of Si:Er and Si:Dy layers in argon are the erbium-related lines. A comparative analysis of the luminescence spectra of the Si:Er and Si:Dy layers shows that the highest intensity of dislocation-related luminescence is achieved in the erbium-implanted structures. A significant influence of intrinsic point defects on the structural and optical properties of erbium-and dysprosium-implanted silicon is revealed. Fiz. Tekh. Poluprovodn. 33, 656–659 (June 1999)     

Photoluminescence in silicon implanted with erbium ions at an elevated temperature

Photoluminescence spectra of n-type silicon upon implantation with erbium ions at 600°C and oxygen ions at room temperature and subsequent annealings at 1100°C in a chlorine-containing atmosphere have been studied. Depending on the annealing duration, photoluminescence spectra at 80 K are dominated by lines of the Er³⁺ ion or dislocation-related luminescence. The short-wavelength shift of the dislocation-related luminescence line observed at this temperature is due to implantation of erbium ions at an elevated temperature. At room temperature, lines of erbium and dislocation-related luminescence are observed in the spectra, but lines of near-band-edge luminescence predominate.     

Effect of Boron Impurity on the Light-Emitting Properties of Dislocation Structures Formed in Silicon by Si<Superscript>+</Superscript> Ion Implantation

The effect of boron implantation on the light-emitting properties of dislocation structures formed in silicon by Si⁺ ion implantation with subsequent annealing is studied. It is shown that the implantation of B⁺ ions has a significant effect on the dislocation-related luminescence intensity, spectrum and the temperature dependence of the D1-band intensity. It is found that the temperature dependence is nonmonotonous and involves two regions, in which the D1-band intensity increases with increasing temperature and has two well-pronounced maxima at 20 K and 60–70 K. The maximum at 20 K is associated with the morphological features of the dislocation structure under study, whereas the maximum at 60–70 K is associated with the additional implantation of the boron impurity into the dislocation region of the samples. It is established that the intensities of the experimentally observed maxima and the position of the high-temperature maximum depend on the implanted boron concentration.     

Influence of the orientation of the silicon substrate on the properties of avalanche Si:Er:O light-emitting structures

The influence of the orientation of silicon on the structural and luminescence properties of avalanche light-emitting diodes fabricated by the coimplantation of erbium and oxygen followed by solid-phase epitaxial (SPE) crystallization of the amorphized layer is considered. The luminescence properties are a consequence of the formation of various structural defects during the SPE crystallization: V-shaped dislocations and erbium precipitates form in (100) Si:Er:O layers, and larger structural defects, i.e, twins, are observed in (111) Si:Er:O layers along with an increase in the dislocation density by more than four orders of magnitude in comparison with the (100) orientation. The luminescence properties of avalanche and tunnel light-emitting diodes are also compared. In contrast to tunnel diodes, in avalanche diodes erbium ions are excited in the entire space-charge layer, and the effective excitation cross section of the Er³⁺ ions and their lifetime in the excited state are 3–4 times larger. Fiz. Tekh. Poluprovodn. 33, 660–663 (June 1999)     

Silicon Light-Emitting Diodes with Luminescence from (113) Defects

Semiconductors - Silicon light-emitting diodes with luminescence associated with (113) defects are fabricated by the implantation of 350-keV oxygen ions at a dose of 3.7 × 1014 cm–2 and...     

Dislocation-related luminescence in silicon,caused by implantation of oxygen ions and subsequent annealing

Multiple implantation of oxygen ions with energies of 0.1–1.5 MeV at doses of 7 × 10¹³?2 × 10¹⁴ cm^?2 and subsequent annealing in a chlorine-containing atmosphere at 900°C for 4 h give rise to dislocation-related luminescence in p-Si. A p → n conductivity-type conversion is also observed in this case in the surface layer of Si, which indicates that electrically active donor centers are formed in the process. Preliminary heat treatment of wafers covered with an erbium-doped film of tetraethoxysilane (TEOS) in argon at 1250°C for 1 h does not preclude the appearance of dislocation-related luminescence, but affects the parameters of the dislocation-related lines (peak positions and intensities).     

Deep-level defects in red GaAs1-xPxlight-emitting diodes

A wide variety of deep-level recombination centers have been observed at large concentrations in commercially available red GaAsP light-emitting diode p-n junctions. Similar defects have not been observed in GaP diodes. The characteristics, probable cause, and possible effect on luminescence efficiency of these deep-level defect centers are described.     

Defect transformation study in silicon-on-insulator structures by high-resolution X-Ray diffraction

Silicon-on-insulator (SOI) structures were fabricated by bonding using a new variant of Smart-Cut technology. As-bonded SOI structures are annealed at high temperature (1100°C) for removal of hydrogen, radiation defects and stresses at the bonding interface. The transformation of structural parameters in as-bonded and annealed SOI structures was investigated by high-resolution X-ray diffraction. The large strain observed for as-bonded SOI structures is relaxed during annealing at high temperature and final SOI wafer has strain-free top silicon layer due to defect annealing and viscous flow of SiO₂. FWHM value for SOI film is higher than that for typical silicon single crystal and is caused by mosaic-like structure only.     

Enhancement of Defect Production Rates in <Emphasis Type="Italic">n</Emphasis>-Type Silicon by Hydrogen Implantation Near 270 K

Defect production behavior in hydrogen-implanted n-type silicon has been studied by varying the implantation temperature from 88 K to 303 K. Deep-level transient spectroscopy has been used to reveal electron trap spectra for Schottky diodes fabricated at room temperature after implantation. Metastable defects are observed in addition to vacancy- and hydrogen-related defects. It is found that the production rates of these defects are greatly enhanced by hydrogen implantation near 270 K. It is suggested that hydrogen plays an important role in enhancement of defect production rates, since such defect production behavior is not observed in He-implanted samples.     

Influence of internal mechanical stresses on the characteristics of GaAs light-emitting diodes

A systematic investigation of the influence of internal mechanical stresses on the characteristics of gallium arsenide light-emitting diodes (LED’s) is performed. The LED structures are grown by liquid-phase epitaxy from a confined volume of a melt based on a solution of GaAs in Ga. The melt is doped with silicon or with silicon and tin. It is shown that the magnitude and sign of the internal mechanical stresses in the epitaxial layer are determined by the impurity concentration in the melt. The LED’s fabricated from epitaxial structures with the smallest internal mechanical stresses have the greatest quantum efficiency and the slowest rate of degradation of their parameters. A model of the reorganization of the defect structure of gallium arsenide, which describes the observed phenomena, is proposed. Fiz. Tekh. Poluprovodn. 32, 1393–1398 (November 1998)     

Molecular dynamics study on splitting of hydrogen-implanted silicon in Smart-Cut® technology

Defect evolution in a single crystal silicon which is implanted with hydrogen atoms and then annealed is investigated in the present paper by means of molecular dynamics simulation. By introducing defect density based on statistical average, this work aims to quantitatively examine defect nucleation and growth at nanoscale during annealing in Smart-Cut~ technology. Research focus is put on the effects of the implantation energy, hydrogen implantation dose and annealing temperature on defect density in the statistical region. It is found that most defects nucleate and grow at the annealing stage, and that defect density increases with the increase of the annealing temperature and the decrease of the hydrogen implantation dose. In addition, the enhancement and the impediment effects of stress field on defect density in the annealing process are discussed.     

Modulation spectroscopy studies of defects

We examine some relationships between defect characteristics and the modulated optical properties of solids. In particular, the effects of an electric field ℰ on the N absorption in GaP are presented. The crystallographic-orientation dependence is used to determine symmetry properties of the impurity electron states and their interaction with the host band structure. These data also yield an impurity concentration which is in agreement (to within a factor of 2) with results obtained using other techniques. The Franz-Keldysh mechanism responsible for the electro-absorption suggests that in indirect gap semiconductors, an electric field should double the luminescence. This enhancement will be greatest for ℰ along the orbital axis of the luminescent center. Generalizations of this work to other chemical and structural defects are discussed.     

Position-Controlled Functionalization of Vacancies in Silicon by Single-Ion Implanted Germanium Atoms

Special point defects in semiconductors have been envisioned as suitable components for quantum-information technology. The identification of new deep centers in silicon that can be easily activated and controlled is a main target of the research in the field. Vacancy-related complexes are suitable to provide deep electronic levels but they are hard to control spatially. With the spirit of investigating solid state devices with intentional vacancy-related defects at controlled position, the functionalization of silicon vacancies is reported on here by implanting Ge atoms through single-ion implantation, producing Ge-vacancy (GeV) complexes. The quantum transport through an array of GeV complexes in a silicon-based transistor is investigated. By exploiting a model based on an extended Hubbard Hamiltonian derived from ab initio results, anomalous activation energy values of the thermally activated conductance of both quasi-localized and delocalized many-body states are obtained, compared to conventional dopants. Such states are identified, forming the upper Hubbard band, as responsible for the experimental sub-threshold transport across the transistor. The combination of the model with the single-ion implantation method enables future research for the engineering of GeV complexes toward the creation of spatially controllable individual defects in silicon for applications in quantum information technology.     

Ion implantation of porous gallium phosphide

The effect of irradiation by Ar ions and thermal annealing on the properties of porous gallium phosphide (por-GaP) obtained by electrolytic methods is investigated. It is shown on the basis of Raman scattering and photoluminescence data that, in contrast with porous silicon, por-GaP does not have high radiation hardness, and that thermal annealing of defects in layers amorphized by ion implantation is impeded by the absence of a good crystal base for solid-state epitaxial recrystallization processes. Data on radiation-induced defect formation and from probing of the material with a rare-earth “luminescence probe” are consistent with a mesoporous structure of the material. Fiz. Tekh. Poluprovodn. 32, 990–994 (August 1998)     

Si:Si LEDs with room-temperature dislocation-related luminescence

Silicon-based light-emitting diodes (LEDs) fabricated by the Si-ion implantation and chemical-vapor deposition methods are studied. Room-temperature dislocation-related electroluminescence (EL) is observed in LEDs based on n-Si. In LEDs based on p-Si, the EL is quenched at temperatures higher than 220 K. The EL-excitation efficiencies are measured for the D1 line at room temperature and the D1 and D4 lines at liquid-nitrogen temperature.     

On the fractal nature of light-emitting structures based on III–N nanomaterials and related phenomena

It is shown that a three-dimensional fractal–percolation system is formed in nanomaterials of light-emitting InGaN/GaN and AlGaN/GaN structures in the presence of conducting extended defects and local inhomogeneities of the composition of the solid solutions; this system determines the electrophysical properties of light-emitting diodes fabricated on the basis of these structures. The geometry and properties of this system depend nonlinearly on the degree of disorder in the nanomaterial of the structures, on the value of the injection current, and on the rate of alloy growth.     

Charge state of luminescence centers in the Si-SiO<Subscript>2</Subscript> structures subjected to sequential implantation with silicon and carbon ions

Electroluminescence of Si-SiO₂ structures subjected to sequential implantation of silicon and carbon ions and to postimplantation annealing is studied. It is shown that two bands appear in the electroluminescence spectrum with energies of 2.7 and 4.3 eV as a result of ion implantation. After annealing, the band peaked at the energy of 3.2 eV appears in the spectrum; this band can be related to the formation silicon-carbide clusters. Charge characteristics of the structures under study are obtained. It is shown that the luminescence centers responsible for all bands are not charged.     

Defects in annealed 1.5 MeV boron implanted p-type silicon

Effects of temperature and dosage on the evolution of extended defects during annealing of MeV ion-implanted Czochralski (CZ) p-type (001) silicon have been studied using transmission electron microcopy. Excess interstitials generated in a 1 10¹⁵ cm⁻²/1.5 MeV B⁺ implanted Si have been found to transform into extended interstitial {311} defects upon rapid thermal annealing at 800°C for 15 sec. During prolonged furnace annealing at 960°C for 1 h, some of the {311} defects grow longer at the expense of the smaller ones, and the average width of the defects seems to decrease at the same time. Formation of stable dislocation loops appears to occur only above a certain threshold annealing temperature (∼1000°C). The leakage current in diodes fabricated on 1.5 MeV B⁺ implanted wafers was found to be higher for a dosage of 1 10¹⁴cm⁻² and less, as compared to those fabricated with a dosage of 5 10¹⁴ cm⁻² and more. The difference in the observed leakage current has been attributed to the presence of dislocations in the active device region of the wafers that were implanted with the lower dosage.