Oxygen Defects In Silicon Research Articles

Formation and dissociation reactions of complexes involving interstitial carbon and oxygen defects in silicon

We present a detailed first-principles study which explores the configurational space along the relevant reactions and migration paths involving the formation and dissociation of interstitial carbon-oxygen complexes, $\mathrm{C_{i}O_{i}}$ and $\mathrm{C_{i}O_{2i}}$, in silicon. The formation/dissociation mechanisms of $\mathrm{C_{i}O_{i}}$ and $\mathrm{C_{i}O_{2i}}$ are found as occurring via capture/emission of mobile $\mathrm{C_{i}}$ impurities by/from O-complexes anchored to the lattice. The lowest activation energies for dissociation of $\mathrm{C_{i}O_{i}}$ and $\mathrm{C_{i}O_{2i}}$ into smaller moieties are 2.3 eV and 3.1 eV, respectively. The first is compatible with the observed annealing temperature of $\mathrm{C_{i}O_{i}}$ , which occurs at around 400 $^{\circ}$C, and below the threshold for $\mathrm{O_{i}}$ diffusion. The latter exceeds significantly the measured activation energy for the annealing of $\mathrm{C_{i}O_{2i}}$ ($E_{\mathrm{a}}=2.55$ eV). We propose that instead of dissociation, the actual annealing mechanism involves the capture of interstitial oxygen by $\mathrm{C_{i}O_{2i}}$, thus being governed by the migration barrier of $\mathrm{O_{i}}$ ($E_{\mathrm{m}}=2.53$ eV). The study is also accompanied by measurements of hole capture cross sections and capture barriers of $\mathrm{C_{i}O_{i}}$ and $\mathrm{C_{i}O_{2i}}$. In combination with previously reported data, we find thermodynamic donor transitions which are directly comparable to the first-principles results. The two levels exhibit close features, conforming to a model where the electronic character of $\mathrm{C_{i}O_{2i}}$ can be described by that of $\mathrm{C_{i}O_{i}}$ perturbed by a nearby O atom.

The spectroscopic characterization of interstitial oxygen in bulk silicon: A quantum mechanical simulation.

The vibrational Infrared and Raman spectra of six interstitial oxygen defects in silicon containing a Si-O-Si bridge between adjacent Si atoms are obtained from all-electron B3LYP calculations within a supercell scheme, as embodied in the CRYSTAL code. Two series of defects have been considered, starting from the single interstitial defect, O1. The first consists of four defects, O1,n, in which two O1 defects are separated by (n - 1) Si atoms, up to n = 4. The second consists of four defects, On, in which nO1 defects surround a single Si atom, with n = 1-4, where O4 has the same local nearest neighbor structure as α-quartz. For both series of defects, the equilibrium geometries, charge distributions, and band structures are reported and analyzed. The addition of 1-4 oxygen atoms to the perfect lattice generates 3-12 new vibrational modes, which, as a result of the lighter atomic mass of O with respect to Si, are expected to occur at wavenumbers higher than 521 cm-1, the highest frequency of pristine silicon, thereby generating a unique new Raman spectrum. However, only a small subset of these new modes is found in the spectrum. They appear at 1153 cm-1 (O1), at 1049 cm-1 and 1100 cm-1 (O1,2), at 1108 cm-1 (O1,3), at 1130 cm-1 and 1138 cm-1 (O1,4), and 773 cm-1, 1057 cm-1, and 1086 cm-1 (O4), and can be considered "fingerprints" of the respective defects, as they are sufficiently well separated from each other. Graphical animations indicate the nature and intensity of each of the observed modes which are not overtones or combinations.

Phosphorous–vacancy–oxygen defects in silicon

Electronic structure calculations employing the hybrid functional approach are used to gain fundamental insight in the interaction of phosphorous with oxygen interstitials and vacancies in silicon. It recently has been proposed, based on a binding energy analysis, that phosphorous–vacancy–oxygen defects may form. In the present study we investigate the stability of this defect as a function of the Fermi energy for the possible charge states. Spin polarization is found to be essential for the charge neutral defect.

Photoluminescence from triplet states of isoelectronic bound excitons at interstitial carbon-intersititial oxygen defects in silicon

Photoluminescence from triplet states of isoelectronic bound excitons at interstitial carbon-intersititial oxygen defects in silicon

Photoluminescence from triplet states of isoelectronic bound excitons at interstitial carbon-intersititial oxygen defects in silicon

We report luminescence from spin triplet states of excitons bound to interstitial carbon-interstitial oxygen defects in silicon. The peak, which we call CT-line, has an energy 2.64 meV lower than 790 meV (C-line), and splits into three peaks by application of magnetic field. Moreover, its peak position does not depend on the angle between the magnetic field direction and crystallographic orientation indicating the quenching of orbital angular momentum of the hole bound to the defect. These observations lead us to conclude that the CT-line is the photoluminescence from a triplet state.

Oxygen defect in silicon studied by semi-empirical calculations

The atomic and electronic structure of interstitial oxygen in bulk silicon is studied by a semi-empirical Hartree--Fock technique. The calculations are performed in real space on a hydrogen terminated cluster in combination with a new parameterization of oxygen within the framework of the modified neglect of diatomic overlap (MNDO) technique. We find that the results on the silicon cluster are in good agreement with experiment as well as with the results of ab initio calculations. Moreover, the various charge states of the oxygen have been analyzed. It has been found that interstitial oxygen in both neutral and double negative charge state forms a stable configuration but the single negative state forms an instable configuration with a strong level in the band gap at E v +0.55 eV.

First-principles study on the local vibrational modes of nitrogen–oxygen defects in silicon

In this paper we investigate the interaction of nitrogen and oxygen by means of local density functional theory. While nitrogen-pair-oxygen defects ( N 2 – O m ) have been studied in detail previously, the existence and role of nitrogen–oxygen defects containing only one nitrogen atom (N– O n ) is still controversial. Motivated by recent infrared absorption measurements, where several new absorption lines were observed, we present first-principles studies on the ground state configuration, binding energy and local vibrational modes of NO and NO 2 . We suggest that the NO 2 defect gives rise to the experimentally observed lines at 1002, 973 and 855 cm - 1 .

Modified neglect of diatomic overlap parametrization of oxygen: A cluster study of oxygen defects in silicon

We present a parametrization of oxygen within the framework of the modified neglect of diatomic overlap (MNDO) technique. The atomic structure and formation energy of a oxygen defect in silicon are studied as a test of the reparametrized MNDO technique. We find that the geometry and the associated formation energy are in good agreement with experiment as well as with results of ab initio calculations. Even the calculations based on the MNDO technique are by 2 or 3 orders of magnitude less expensive than ab initio calculations.

Local vibrations of thermal double donors in silicon

The local vibrational modes (LVM's) of the oxygen chains assigned to thermal double donors (TDD's) and other related oxygen defects in silicon are studied using accurate total-energy calculations. We find that the calculated LVM frequencies as well as their isotopic shifts and charge-state dependences (temperature dependences) for the oxygen chains agree closely with the corresponding experimental quantities, which supports our assignments of the ${\mathrm{O}}_{2i}\ensuremath{-}{\mathrm{O}}_{2r}$ chain to TDD1 and the ${\mathrm{O}}_{i}\ensuremath{-}{\mathrm{O}}_{\mathrm{nr}}\ensuremath{-}{\mathrm{O}}_{i}$ chains to $\mathrm{TDD}n$ $(n>1)$ $({\mathrm{O}}_{i}$ is an interstitial oxygen and ${\mathrm{O}}_{r}$ a threefold coordinated oxygen belonging to a ring).

First principles study of oxygen defects in silicon

Large scale electronic structure calculations are used to study atomic and electronic structures of oxygen complexes O n (1⩽ n⩽14) and their migration and isomerization in crystalline silicon. Total energies, atomic geometries, charge states, and ionization levels are investigated for the various types of defects. The thermodynamic and the kinetic behaviours of defects are discussed on the basis of the first principles results. The chain-like structures are energetically more favorable than branched ones. The migration energies of the chain-like structures are 0.3 ∼ 2.3 eV and those of branched ones are 2.3 ∼ 2.5 eV. The activation barriers for the isomerizations between different structures are about 2.3 ∼ 2.5 eV.

Phonon spectroscopy of oxygen defects in silicon and germanium

Oxygen as an impurity in Si and Ge and in III-V-compounds such as GaAs or GaP has been an object of research since decades because of its complicated incorporation as well as its technical relevance. Phonon spectroscopy with superconducting tunnel junctions by its high sensitivity, good resolution, and convenient tunability is most appropriate for the investigation of the low-energy vibrational states of the interstitial oxygen as well as of the various nanoscopic precipitates with dimensions of the size of the phonon wavelength.

The nitrogen-pair oxygen defect in silicon

The nitrogen-pair oxygen defect in silicon has been studied by infrared absorption spectroscopy on samples implanted with various combinations of 14N, 15N, 16O and 17O. The measurements give direct evidence for the involvement of nitrogen and oxygen in the defect and show that the impurity atoms comprising the defect are only weakly coupled. Ab initio cluster calculation on several models of the nitrogen-pair oxygen defect have been performed and are compared with experiment. Based on these investigations a model consisting of a bridging oxygen atom adjacent to the nitrogen pair is suggested.

Electrical characters of oxygen defects in silicon subjected to intrinsic gettering treatment

The influence of oxygen defects on the resistivity and mobility of silicon wafers is discussed. Grinding processes were performed on the surfaces of samples in order to obtain the information on interior defects of the samples. Spreading resistivity and Hall measurements prove that SiOx complexes alone result in resistivity increase and mobility decrease. Deep level transient spectroscopy experiments prove that SiOx complexes alone are electrically active. A mechanism of carrier scattering by electrically active SiOx complex is proposed to explain the changes of resistivity and mobility.

Hall effect spectroscopy of thermal donors in silicon films synthesized by oxygen implantation

The electrical properties of silicon layers formed by implantation of oxygen (SIMOX) are controlled by oxygen thermal donors (TDs) which are activated in a high density (10 15–10 16 cm −3) during technological processes. It has been found that 650°C is the annealing temperature at which TDs are activated in the lowest density. The conventional Hall effect analysis consists of deriving the electrical TD ionization energy from the activation energy in the Arrhenius plot of n vs. 1/T. However, it is well known that this method is not very accurate in the case of oxygen defects in silicon since many levels coexist. Thus, we propose a spectroscopic analysis of Hall effect measurements based on a differential evaluation of the n vs. 1/T characteristics which clearly reveals the existence of TDs in SIMOX thin films. The films annealed at 650°C for 1 h showed only deep TD levels (240 and 300 meV), whereas shallow TD levels (45–65 meV) were activated in arsenic-implanted films. These TD levels, which were not detected in the conventional analysis, were responsible for an apparent decrease in the activation energy in the high temperature range.