1,721,008 research outputs found
Ion beam characterization of Fe implanted GaN
No full textFe ion implantation in GaN has been investigated by means of ion beam analysis techniques. Implantations at an energy of 150 keV and fluences ranging from 2 x 10^15 to 1 x 10^16 cm^-2 were done, both at room temperature and at 623 K. Secondary Ions Mass Spectrometry was used to determine the Fe implantation profiles, whereas Rutherford Backscattering in channeling conditions with a 2.2 MeV 4He^+ beam allowed us to follow the damage evolution. Particle Induced X-ray Emission in channeling conditions with a 2 MeV H+ beam was employed to study the lattice location of Fe atoms after implantation. The results show that a high fraction of Fe-implanted atoms are located in high symmetry sites in low fluence implanted samples, where the damage level is lower, whereas the fraction of randomly located Fe atoms increases by increasing the fluence and the resulting damage. Moreover, dynamical annealing present in high temperature implantation has been shown to favor the incorporation of Fe atoms in high symmetry sites
Structural characterization of light elements in semiconductor materials by means of selected nuclear reactions
No full textMaterials and structures for microelectronics are characterized by a continuous decrease of their dimensions. Nanostructured materials are currently required to design and produce novel devices. We will show that, in spite of their relatively poor lateral resolution, selected nuclear reactions or ad-hoc studied resonances in the elastic cross section of alpha particles, in random and channelling configuration, can accurately quantify and provide the lattice location of different light elements in various semiconductor matrices. Different systems of current interest will be described. Moreover physical results obtained by combining nuclear reactions with Rutherford BackScattering (RBS), High Resolution X-Ray Diffraction (HRXRD) and Secondary Ion Mass Spectrometry (SIMS) analysis will be discussed.
In particular the relation between the lattice parameter and the light impurity concentration in the case of Si-C ,Si-Ge-C ,Ga-As-N-(In) dilute alloys and of B-doped silicon will be described. We will also show some results on hydrogenated (deuterated) dilute nitrides
Carrier mobility and strain effect in heavily doped p-type Si
No full textAlthough carrier mobility (μ) in Si is a fundamental property deeply investigated since 40 years, a complete understanding of its characteristics over a large range of carrier concentration is still lacking. For example, the effect of strain was largely debated and μ enhancement was demonstrated in strained Si channels where the carrier concentration is 10^20 cm−3), which is actually of fundamental interest for USJ applications, many questions are still open about μ: why is μ lower in presence of some dopants with respect to other chemical species? The relevant point is that high μ in either n- or p-type Si is observed when the dopant has a covalent radius smaller than Si and that, at the concentration at which the chemical effect on the μ is visible, an appreciable strain is generated in the doped layer. We present here an experiment to study the dependence of the hole μ on the dopant species in heavily doped p-type Si under low electrical field. The Hall carrier concentration and μ has been measured in Si co-implanted with B and Ga in the (0.1–2) × 10^20 cm−3 range. The strain induced by substitutional dopants, detected by high resolution X-ray diffraction (HRXRD), has been varied by changing the B and Ga concentration. The effect of strain on μ has been disentangled and a linear dependence of 1/μ on the perpendicular strain has been found. Using this relationship we demonstrate that the strain induced by the substitutional dopant can account for the effect of chemical species on charge carrier μ
Iso-concentration study of atomistic mechanism of B diffusion in Si
No full textB diffuses in crystalline Si by reacting with Si self-interstitial (I) with a frequency g, forming a BI complex that can migrate for an average length lambda. We experimentally measured both g and lambda as a function of the hole concentration p by means of iso-concentration experiments on B delta-layers both under p- and n-doping conditions. On the basis of these data, we propose a comprehensive model that fixes the interplay among free charge, I and BI charge states that determines the B diffusion. Pairing effect with donors was also considered. (C) 2007 Elsevier B.V. All rights reserved
High-level incorporation of antimony in germanium by laser annealing
No full textIn this work we investigate pulse laser annealing as an alternative approach to reach high-level incorporation of Sb in substitutional location in crystalline germanium. Laser irradiation is demonstrated to recover also those structural defects, like honeycomb structures, that form during high-fluence heavy-ion implantations in Ge and that cannot be eliminated by conventional thermal treatments. Indeed, concentrations of substitutional Sb higher than 1×1021 at./cm3 have been obtained, well above the solid solubility of Sb in Ge. The strain induced on the Ge host lattice is also investigated, evidencing that the obtained Sb doped Ge layer is pseudomorphic to the Ge substrate while positively strained by the substitutional Sb atoms present within the Ge matrix. The kinetics of this Sb-rich Ge alloy phase is finally investigated, showing that most of Sb goes out of lattice with increasing the annealing temperature up to 488 °C, leading to a decrease in the related lattice deformation. These results are very relevant for the future high-mobility channel technology
Substitutional and clustered B in ion implanted Ge: Strain determination
No full textThe lattice strain induced both by substitutional and clustered B in B-implanted Ge samples has
been investigated by means of high resolution x-ray diffraction HRXRD. The main results can be
summarized as follows: while substitutional i.e., electrically active B exhibits a negative strain,
clustered i.e., electrically inactive B reverses the lattice strain from negative to positive values, the
latter being much higher with respect to those found for clustered B in Si. In particular, the lattice
volume modification for each B atom V induced by substitutional VSub and clustered VCl
B is VSub=−12.4 Å3 and VCl=+14.8 Å3, respectively. These unexpected results demonstrate the
ability of HRXRD to quantitatively detect the amount of electrically inactive and active B
Strain relaxation of SiGe in a Si/SiGe/Si heterostructure under proton irradiation
No full textWe have studied the mechanisms underlying strained layer relaxation by means of point defect
interaction. During high temperature 300 °C proton irradiation, vacancies generated in the vicinity
of SiGe layer migrate and accumulate within the compressively strained SiGe layer. The
accumulating vacancies are stabilized by hydrogen, which diffuses from the implanted region, thus
allowing the nucleation and growth of hydrogen-vacancy V-H complexes. The formation of V-H
complexes is accompanied by gradual strain relief in SiGe layer. Since the diffusion of both
vacancies and hydrogen is limited by the irradiation temperature, strain relaxation of the SiGe layer
is not realized during room temperature 20 °C proton irradiation. The study supports the idea that
the compressive stress in the SiGe layer induces the indiffusion of vacancies and H, and reveals the
important role of point defects in the strain relaxation of the strained SiGe layer
Effect of strain on the carrier mobility in heavily doped p-type Si
No full textWe present an experiment that gives insight into the origin of the dependence of the hole mobility (mu) on the dopant species in heavily doped p-type Si under low electrical field. The Hall carrier concentration and mobility were measured in Si coimplanted with B and Ga in the 0.1-2x10(20) cm(-3) concentration range. The strain induced by substitutional dopants, detected by high resolution x-ray diffraction, was varied by changing the relative B and Ga concentration. The effect of strain on mobility was disentangled and a linear relationship between 1/mu and the perpendicular strain was found
Atomistic Mechanism of Boron Diffusion in Silicon
Full text linkB diffuses in crystalline Si by reacting with a Si self-interstitial (I) with a frequency g and so forming a fast migrating BI complex that can migrate for an average length λ. We experimentally demonstrate that both g and λ strongly depend on the free hole concentration p. At low p, g has a constant trend and λ increases with p, while at high p, g has a superlinear trend and λ decreases with p. This demonstrates that BI forms in the two regimes by interaction with neutral and double positive I, respectively, and its charge state has to change by interaction with free holes before diffusing
On the Strain Induced by Arsenic into Silicon
No full textThe strain induced by substitutional arsenic into the silicon lattice was investigated experimentally. First, a combination of multiple implantations was used to obtain a flat arsenic profile in the first 150 nm of the substrate. Although a full activation of the dopants could be achieved, the EOR defects resulting from the implants were not dissolved and prevented reliable strain measurements. A single implantation was then used. Annealing conditions were carefully chosen to obtain a nearly flat arsenic profile in the first 400 nm of the substrate and to dissolve the EOR defects. Sheet resistance, TEM and RBS measurements confirmed the full activation of the samples and the dissolution of the EOR defects. HRXRD was then used to characterize the strain. The interpretation of the measurements via strain simulation indicated a lattice strain of (-1.5 +/- 0.7)x10(-5) associated with a lattice contraction at a concentration of 2x10(20) cm(-3). This value is significantly lower than the values reported in literature
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