Erbium Implantation Research Articles

Silicon shallow doping by erbium and oxygen recoils implantation

Abstract In order to get shallow high doping of Si with optically active complexes ErOn, Er followed by O recoils implantation was realized by means of subsequent Ar+ 250–290 keV implantation with doses 2×1015–1×1016 cm–2 through 50-nm deposited films of Er and then SiO2, accordingly. High Er concentration up to 5×1020 cm−3 to the depth of 10 nm was obtained after implantation. However, about a half of the Er implanted atoms become part of surface SiO2 during post-implantation annealing at 950 °С for 1 h in the N2 ambient under a SiO2 cap. The mechanism of Er segregation into the cap oxide following the moving amorphous–crystalline interface during recrystallization was rejected by the transmission electron microscopy (TEM) analysis. Instead, the other mechanism of immobile Er atoms and redistribution of recoil-implanted O atoms toward cap oxide was proposed. It explains the observed formation of two Er containing phases: Er–Si–O phase with a high O content adjacent to the cap oxide and deeper O depleted Er–Si phase. The correction of heat treatments is proposed in order to avoid the above-mentioned problems.

Ion implantation of erbium into polycrystalline cadmium telluride

The specific features of the ion implantation of polycrystalline cadmium telluride with grains 20–1000 μm in dimensions are studied. The choice of erbium is motivated by the possibility of using rare-earth elements as luminescent “probes” in studies of the defect and impurity composition of materials and modification of the composition by various technological treatments. From the microphotoluminescence data, it is found that, with decreasing crystal-grain dimensions, the degree of radiation stability of the material is increased. Microphotoluminescence topography of the samples shows the efficiency of the rare-earth probe in detecting regions with higher impurity and defect concentrations, including regions of intergrain boundaries.

Erbium Emission from Nanoengineered Silicon Surface

Optically active SiOx nanowires were grown on silicon by ion-implanting it with metallic impurities and annealed at 1100 °C in an Ar ambient. The implanted metals precipitate on the silicon surface and act as catalysts for nanowire growth. Ion implantation of erbium into silicon and subsequent heating in an argon ambient resulted in selective nucleation and growth of optically active silica nanowires. The bottom-up nanowire growth, mediated by vapor liquid solid mechanism, was also demonstrated for a multimetal (Au:Er) implant combinations in Si. The role of Er as a catalyst and dopant resulted in optically active silica nanowires that exhibited photoluminescence emission at 1.53 μm from an Er3+ intra-4f transition. Time resolved photoluminescence (PL) from these nanostructures indicated a luminescence lifetime of 24 ms, larger than that generally observed for Er-doped bulk silica. This increase in luminescence lifetime is attributed to a reduction in the optical density of states of Er in the nanowire sa...

Erbium implantation in silica studied by molecular dynamics simulations

Defect formation induced by erbium implantation in silica glass and cristobalite was studied using molecular dynamics simulations employing a partial charge model in combination with the ZBL potential. The results show that the number of displaced atoms generated at the same PKA energy is similar in silica and cristobalite but the number of coordination defects created is much lower in the cristobalite than in silica glass. In both cases, the erbium ion is able to create an optimal coordination environment at the end of the collision cascade. Subsequent thermal annealing causes the relaxation of the silicon oxygen network structure along with a reduction of silicon and oxygen defects.

Defect accumulation during channeled erbium implantation into GaN

Gallium nitride films epitaxially grown on sapphire, were irradiated at room temperature with 80keVEr+166 or 170keVEr2+166 ions to fluences ranging from 1×1013cm−2 to 1×1015cm−2. The defects induced by ion implantation (as a result of the nuclear energy transfer) generate a perpendicular elastic strain in the hexagonal GaN lattice. The accumulation of lattice damage and lattice deformation were investigated for Er ions impinging along the GaN⟨0001⟩ axis, i.e., channeled implantation, and compared to random implantation, i.e., the conventional geometry in which the ion beam is tilted 10° off the GaN c axis. For this purpose, Rutherford backscattering and channeling spectrometry and high-resolution x-ray diffraction were used. The defect concentration and the maximum perpendicular strain exhibit the same increasing trend with the ion fluence. Three regimes can be distinguished for both implantation geometries, for low fluences (corresponding to a value below 1 displacement per atom in case of random implantation), the defect concentration remains low due to an effective dynamic annealing process. In the second fluence regime, the defect concentration rises sharply, which is characteristic for nucleation-limited amorphization and finally, a third regime is found where layer-by-layer amorphization of the implanted area starts from the surface. The onset of the steep increase in the case of implantations along the GaN c axis is found at a significantly higher erbium fluence compared to random implantation.

Effect of current on the electroluminescence of defects produced by high-temperature post-implantation annealing of Si: (Er,O) structures in a chlorine-containing environment

The forward-current dependence of defect-related electroluminescence (EL) in silicon structures produced by erbium and oxygen implantation into silicon single crystals with subsequent annealing in a chlorine-containing ambient at 1100°C has been studied. At 80 K, an increase in the current was observed to cause the photon energies corresponding to the maxima of two defect-related EL peaks to increase from 0.807 and 0.87 eV to 0.85 and 0.92 eV, respectively. The increase in the current was also accompanied by an increase in the half-width and intensity of the EL peaks. To explain the observed effects, a model that was proposed earlier for the defect-related EL in plastically deformed silicon is developed further; this model assumes the possible generation of inverse population involving four energy levels.

Photoluminescence ofEr3+-implanted amorphous hydrogenated silicon suboxides

Erbium ions incorporated into amorphous hydrogenated silicon suboxides $(a\ensuremath{-}{\mathrm{SiO}}_{x}:\mathrm{H})$ allow to overcome the disadvantages of ${\mathrm{Er}}^{3+}$ in $c\ensuremath{-}\mathrm{Si}$ such as the limited solubility, the strong quenching of the luminescence at room temperature, and the need for co-doping with electronegative atoms. $a\ensuremath{-}{\mathrm{SiO}}_{x}:\mathrm{H}$ alloys have an enhanced Er solubility and easily variable oxygen content, thereby providing favorable atomic environments for an efficient Er luminescence and reduced excitation backtransfer due to deeper localized band-tail states. In the present study, ${\mathrm{Er}}^{3+}$ doses up to $7\ifmmode\times\else\texttimes\fi{}{10}^{14}{\mathrm{cm}}^{\ensuremath{-}2}$ were implanted into a-${\mathrm{SiO}}_{x}:\mathrm{H}$ with oxygen content between 0 and 44 at. %. Optical properties such as the absorption coefficients and the photoluminescence (PL) spectra of the ${\mathrm{Er}}^{3+}$ ions and of the ${\mathrm{SiO}}_{x}$ host were investigated as a function of erbium implantation dose, oxygen content, defect density, temperature, and annealing treatment. It was found that annealing is a requirement for activating the characteristic Er PL at 1.54 \ensuremath{\mu}m mainly due to a reduction of implantation induced defects. The intensity of both the intrinsic ${\mathrm{SiO}}_{x}$ and the Er PL was found to be inversely proportional to the defect density as measured by electron spin resonance or subgap absorption. The Er PL is additionally enhanced upon annealing, probably as a result of better structural arrangements of the Er ions. The Er PL intensity increases approximately linearly with the implantation dose. An increase of the oxygen content (and correspondingly of the optical band gap) of $a\ensuremath{-}{\mathrm{SiO}}_{x}:\mathrm{H}$ causes no drastic changes in the erbium luminescence energy and intensity, whereas the intrinsic PL shifts to higher photon energies according to the larger band gap. Already low O concentrations of a few percent provide favorable Er environments. The main advantage of $a\ensuremath{-}{\mathrm{SiO}}_{x}:\mathrm{H}$ as a host matrix is revealed by temperature-dependent PL measurements. For high oxygen contents, the thermal quenching of both the ${\mathrm{Er}}^{3+}$ and the intrinsic PL is strongly reduced. In an $a\ensuremath{-}{\mathrm{SiO}}_{x}$ sample with 44 at. % oxygen, the Er PL is only quenched by 20% between 77 and 300 K. In contrast, the quenching of the intrinsic PL for all [O] is roughly one order of magnitude stronger than that of the Er PL. These PL measurements were complemented by PL excitation experiments over a wide spectral range. We have observed that the ${\mathrm{Er}}^{3+}$ PL is excited about one order of magnitude more efficiently when pumped with sub-band-gap light compared to band-to-band excitation. The experimental results are discussed with regard to the two currently proposed ${\mathrm{Er}}^{3+}$ excitation models, the defect-related Auger effect and the F\orster transfer mechanism.

Electrical and structural characterization of defects introduced in p-SiGe during low energy erbium implantation

We have used electrical measurements Deep level transient spectroscopy (DLTS) complemented by high-resolution X-ray diffraction (HRXRD) and Rutherford backscattering spectroscopy (RBS) measurements for assessment of the defects introduced in p-Si 1− x Ge x during 160 keV erbium ion implantation. From deep-level transient spectroscopy, it was observed that two prominent defects with discrete energy levels above the valence band, were introduced during Er ion implantation. The observed defects have similar signatures as those introduced during α-particle irradiation and electron beam metal deposition, indicating that these defects are more likely not related to Er but only to implantation induced damage such as primary defects. The generated defects expand the Si 1− x Ge x lattice in the implanted region, which results in the presence of the tail in the high-resolution X-ray diffraction spectra. After rapid thermal annealing (RTA) at 850 °C for 30 s in nitrogen ambient, a reduction in defect density as well as a relaxation of the Si 1− x Ge x lattice is observed for all x values. A dominant Er-related sharp emission in the 1.54 μm region was observed at room temperature and neither the intensity of the Er emission nor the emission peak position were influenced by the Ge content or the strain relaxation in the epilayers.

Effects of substrate temperature and annealing temperature on the formation and properties of erbium silicide layers synthesized by high current Er ion implantation

Ion beam synthesis of ErSi2−x by erbium implantation into Si wafers with a metal vapor vacuum arc (MEVVA) ion source has been performed and the effects of substrate temperature and annealing temperature on its properties have been investigated. The implantation was performed at an extraction voltage of 60 kV to ion doses ranging from 5×1016 to 2×1017 cm−2 with beam current densities from 3 to 26 μA/cm2 corresponding to substrate temperatures ranging from 85 to 245 °C. The characterization of the as-implanted and annealed samples was performed using Rutherford backscattering spectrometry, x-ray diffraction, atomic force microscopy, and electrical resistivity measurements. The results showed that ErSi2−x phase was directly formed by MEVVA implantation when the substrate temperature Ts⩾200 °C. For the samples synthesized at lower implantation temperatures, postimplantation annealing is necessary to achieve the formation of ErSi2−x. Direct measurements of the sputtering depth on masked implanted samples at various substrate temperatures showed that the sputtering yield increases with increasing temperature. The intensive sputtering and aggregation due to high substrate temperatures result in surface fractal patterns, in some cases, discontinuous layers, thus the high resistivity of the layers.

Erbium-doped optical waveguide materials based on Si nanocrystals formed bymetal vapour vacuum arc ion implantation

Dual implantation of erbium and silicon into thermally grown SiO2 film on Siwas performed using a metal vapour vacuum arc ion source; this wasfollowed by rapid thermal annealing at 500–1100°C for 20 s. 1.54 μ mphotoluminescence (PL) was observed at 77 K. Rutherford backscatteringspectrometry shows that Er ions mainly distribute within 80 nm of thesurface. The highest Er peak concentration obtained exceeded 5 × 1021 cm−3,which is the highest Er concentration reported in Si-based materials.Transmission electron microscopy demonstrates that nanocrystallinesilicon (nc-Si) embeds in SiO2 matrices. The Er3 + excitation energy isobtained from the electron–hole pairs nonradiatively combining at defectsand impurities in SiO2 matrices or at the interface of the nc-Si/SiO2(or c-Si/SiO2), and energy transferring to Er3 + ions results in 1.54 μ mlight emission. The dependence on the Si-ion dose and annealing temperature ofthe PL intensity has also been investigated.

Capacitance-voltage characteristics of p-n structures based on (111)Si doped with erbium and oxygen

Capacitance-voltage characteristics of tunneling diodes fabricated by co-implantation of erbium and oxygen in single-crystal (111)Si wafers have been studied. Anomalous enhancement of the p-n-junction capacitance with increasing reverse bias has been observed at certain temperatures depending on the implantation dose. The rise in capacitance (decrease in the space charge region width) is associated with the formation of deep levels of high density in the band gap of n-layer of the p-n junction and electron emission from these levels in the space charge region with increasing voltage. The obtained results show that the parameters of the defects responsible for the levels depend on the erbium and oxygen implantation doses.

PHOTOLUMINESCENCE OF ERBIUM-DOPED HYDROGENATED AMORPHOUS SiOx(0<x<2)

Hydrogenated amorphous SiOx films are fabricated via plasma enhanced chemical vapor deposition technique. After erbium implantation and rapid thermal annealing, photoluminescence (PL) are measured at 77K and room temperature (RT) , respectively. We observed the strong PL at 1.54μm at RT. The 1.54μm PL inten sity changes with the variation of concentration of oxygen. The most intense PL at 77K in a-SiOx∶H (Er) corresponds to O/Si=1.0 and at RT to O/Si=1. 76. Based on our results, we propose that Er ions contributed to PL come from O- rich region in the film. Er ions in Si-rich region have no relation with PL. Tem perature dependence of the intensity of the 1.54μm line of the Er3+ transition displays a very weak temperature quenching in Er-doped hydrogenated a morphous Si. The PL intensity at 250K is a little more one half of that at 15K.

High-Fluence Implantation of Erbium into Silicon-Germanium Alloys: Structural and Thermal Properties

AbstractHigh-quality crystalline Si1-xGex (x=0.10 and 0.25) alloys were implanted with 70 keV Er+ ions at temperatures of 350°C and 550°C to a fluence of 1015 cm−2. In-situ Rutherford backscattering/channeling (RBS) analysis supplemented with transmission electron microscopy (TEM) showed that as-implanted alloys were in form of ternary solid solutions with a peak Er concentration of 1 at.% without any trace of Er-Si or Er-Ge precipitation.In the samples implanted at 350°C Er atoms were found to be distributed randomly in the amorphous host matrix. Post-implantation annealing at different temperatures up to 600° showed that the solid phase epitaxial regrowth of the damaged layers strongly depends on both the Ge concentration in the alloys and the temperature of annealing. Along with the recrystallization of the damaged matrix, annealing was observed to induce simultaneous removal of nearly all the implanted Er as the recrystallization front progresses towards the surface.In contrast, high temperature implantation at 550°C led to spontaneous recovery of the alloy crystallinity and incorporation of considerable fraction of implanted Er atoms on regular tetrahedral interstitial sites in the host lattice.

Oxygen and Erbium related donor centers in Czochralski grown silicon implanted with erbium

The Hall effect measurements were conducted on Czochralski-grown silicon after implantation of erbium and two-step annealing at 700 °C and 900 °C. After the first step the formation of oxygen-related shallow donors was observed at E c in the range 20–40 meV and erbium-related donor centers at ≈E c -70 meV and ≈E c -120 meV. Along with the same oxygen-related shallow thermal donors and donor centers at ≈E c -70 meV, other donor centers at ≈E c -150 meV are formed following the 900°C anneal, instead of those at ≈E c -120 meV. The new donor states are of particular interest because of their possible involvement in the photoluminescence process. The obtained results for erbium-implanted silicon are compared with some fragmentary DLTS data found in the current literature on the donors with ionization energies less than 0.2 eV.

Effect of annealing on the optical and structural properties of GaN:Er

The effect of annealing on the optical and structural properties of gallium nitride layers grown by metalorganic chemical vapor deposition and implanted with 0.8 to 2.0-MeV erbium ions at doses of (1−4)×1014 cm−2 is investigated. Additional implantation of 0.11 to 0.28-MeV oxygen ions at doses of (1−4)×1015 cm−2 is performed on some samples. Measurements of the Rutherford backscattering of protons show that amorphization of the gallium nitride layers does not occur at the erbium implantation doses investigated. The formation of erbium-related luminescence centers which emit at 1.54 µm ends before the defect structure of the implanted layers is restored during a postimplantation anneal in the temperature range 700–1300 °C.

Stress corrosion studies of ion implanted austenitic steel

Stress corrosion studies of 50 Mn18Cr4 austenitic steel implanted with 120 keV N+, 100 keV Cr+, 200 keV and 400 keV Er+ ions were carried out by constant strain method in the nitrate solution. Surface composition and depth profiles of the implanted material were measured by AES sputter etching technique. The results exhibit that nitrogen implantation has no significant affection to the stress corrosion, but the chromium and erbium implantation has prolonged the incubation period of the stress corrosion cracking. (C) 1999 Kluwer Academic Publishers.

Deep level properties of erbium implanted epitaxially grown SiGe

We have used deep-level transient spectroscopy (DLTS) in an investigation of the electronic properties of defects introduced in n-Si 0.96Ge 0.04 during 180 keV erbium ion implantation (fluence= 1 × 10 10 cm −2 ). Five defects with discrete energy levels, ranging from 0.17 to 0.59 eV below the conduction band, were introduced during Er ion implantation. These defects are compared to those introduced during He-ion etching and alpha particle irradiation. By comparing the DLTS spectra and DLTS signatures, it was noted that certain defects (Eer3, Eer4 and Eer5) are only observed in the Er implanted SiGe. Photoluminescence in the 1.54 μm region due to the erbium implantation in Si 0.96Ge 0.04 was observed after a thermal treatment at 900°C for 30 s.

EPR study of erbium-impurity complexes in silicon

Electron paramagnetic resonance (EPR) measurements have been used to characterise Er complexes formed in FZ silicon by the implantation of erbium together with either oxygen or fluorine. The samples have a 2 μm thick layer containing 10 19 Er/cm 3 alone or in addition 3×10 19 O/cm 3, 10 20 O/cm 3 or 10 20 F/cm 3. Various post-implantation anneals were carried out. Several different erbium centres, which have either C 1h monoclinic or trigonal symmetry, are observed and the way in which the type of centre depends on the implantation and annealing conditions is reported.

Dislocation-related luminescence in Er-implanted silicon

The behavior of luminescence spectra and structural defects in single crystal Czochralski silicon after erbium implantation at 1–1.8 MeV energies and 1×10 13 cm −2 dose with subsequent annealing at 1000–1200°C for 0.25–3 h in argon and a chlorine-containing ambience (CCA) was studied by photoluminescence (PL), transmission electron microscopy and chemical etching/Nomarski microscopy. We have found that annealing in CCA gives rise to dislocation loops and pure edge dislocations with dominant dislocation-related lines in the PL spectrum. Pure edge dislocations are responsible for the appearance of the lines.

Erbium implantation in silicon: from materials properties to light emitting devices

Erbium implantation in silicon has recently emerged as a promising method to tailor the optical properties of Si towards the achievement of a light emission at 1.54 μm. In this paper we will review our recent work on this subject. In particular a detailed investigation of the non-radiative processes, competing with the radiative emission of Er in Si will be presented. Among these processes, an Auger de-excitation with the energy released to free carriers will be demonstrated to be extremely efficient, with an Auger coefficient C A~4.4×10 −13 cm 3 s −1. Using the knowledge on the material properties, an efficient Er implanted light emitting diode has been fabricated. It will be shown that by exciting Er within the depletion region of reverse biased p + -n + Si diodes in the breakdown regime it is possible to avoid Auger quenching and to achieve high efficiency. Moreover, at the switch off of the diode, when the depletion region shrinks, the excited Er ions become suddenly embedded within the neutral heavily doped region of the device. In this region Auger de-excitation with free carriers sets in and quenches the luminescence rapidly. This allows modulation of the light emitting devices at frequencies as high as a few MHz. These data will be presented and discussed.