Hydrogen Complexes In Silicon Research Articles

Theory of a carbon‐oxygen‐hydrogen recombination center in n‐type Si

We have recently found that in‐diffusion of hydrogen into n‐type Si crystals containing oxygen and carbon impurities can result in the formation of powerful recombination centers (M. Vaqueiro‐Contreras et al., to appear in PSS RRL). Here, we describe a combination of first‐principles calculations and electrical measurements to investigate the composition, structure, electrical activity and recombination mechanism of a carbon‐oxygen‐hydrogen complex (COH) in Si. We found a defect comprising a carbon‐oxygen complex connected to an H atom whose location depends on the charge state of the complex, and showing a calculated acceptor level at Ev + 0.3 eV, a few meV away from the observations. Bistable carbon–oxygen–hydrogen complex in silicon. Carbon, oxygen, hydrogen, and silicon atoms are shown in gray, red, black, and white, respectively.

Palladium–Hydrogen Complex in Silicon Observed by Electron Spin Resonance Measurement

We have investigated a palladium–hydrogen complex in silicon by electron spin resonance (ESR) measurement. A new ESR spectrum was detected in a sample diffused with palladium and hydrogen. The hyperfine structure of hydrogen atoms in the ESR spectrum shows that the spectrum originates from a palladium–hydrogen complex containing three hydrogen atoms (Pd–H3). The anisotropic g-value of Pd–H3 shows that the Pd–H3 complex has an anisotropic character of orthorhombic (C2v) symmetry. The calculated g-values of the Pd–H3 complex are g1 = 2.12, g2 = 2.10, and g3 = 2.03, and the g2 axis is along the <100 > direction. The anisotropic character of orthorhombic (C2v) symmetry results from a configuration consisting of one Pd atom at a substitutional site, two equivalent hydrogen atoms at interstitial sites along the <111 > direction, and one hydrogen atom at the next-nearest-neighbor interstitial site along the <100 >-twofold symmetry axis. We have also studied the dissociation of a platinum–hydrogen complex by thermal treatment. The activation energy for the dissociation of the Pd–H3 complex is estimated to be about 1.6 eV.

Palladium–Hydrogen Complex in Silicon Observed by Electron Spin Resonance Measurement

Palladium–Hydrogen Complex in Silicon Observed by Electron Spin Resonance Measurement

Correlation between ESR and infrared absorption signals from platinum–hydrogen complexes in silicon

We present results of correlative measurements of platinum–hydrogen (Pt–H) complexes in silicon using infrared absorption (IR) and ESR measurements. Relative concentrations of the complexes in the samples were varied employing various gas pressures during hydrogen doping procedure. The ESR and IR results for the PtH2 and PtH3 complexes showed good correlation in various samples, supporting the existing identification of the IR peaks. The ESR and IR signals assigned to PtH pair, however, behaved differently. Our results suggest that the IR peak assigned previously to PtH pairs only, contains several unresolved components corresponding to PtmH (m⩾1) defects.

Electronic structure of divacancy–hydrogen complexes in silicon

Divacancy–hydrogen complexes(V2H andV2H2)in Si are studied by ab initio modelling using large supercells. Here we payspecial attention to their electronic structure, showing that these defectsproduce deep carrier traps. Calculated electrical gap levels indicate thatV2H2 is an acceptor,whereas V2H is amphoteric, with levels close to those of the well known divacancy. Finally our results arecompared with the available data from deep level transient spectroscopy and electronparamagnetic resonance experiments.

Platinum–hydrogen complexes in silicon observed by measurements of optical absorption and electron spin resonance

Platinum–hydrogen (Pt–H) complexes in Si doped with Pt and H by heating at 1000–1300 °C followed by quenching in water were investigated from the measurements of optical absorption at 5 K and electron spin resonance (ESR) at 8 K. Optical absorption peaks at 1909.1 and 1910.3 cm−1 were observed in addition to the peaks due to the PtH and PtH2 complexes. The H doping temperature dependence of these peaks showed that the number of H atoms in the complex responsible for the 1909.1 cm−1 peak is larger than that for the 1910.3 cm−1 peak. We also observed ESR signals due to the PtH3 complex. The annealing behaviors of the 1910.3 cm−1 peak and the ESR signals were almost the same. Based on these results, the 1909.1 and 1910.3 cm−1 peaks are, respectively, assigned to the PtH4 complex and the PtH3 complex.

Stress-induced splitting of the electronic level related to a platinum–hydrogen complex in silicon

We have applied deep-level transient spectroscopy (DLTS) under uniaxial compressive stress to study the structure of a platinum- and hydrogen-related defect, which has a gap state at 0.14 eV below the conduction band minima in Si. The application of 〈1 0 0〉 and 〈1 1 1〉 stresses split the DLTS peak of the defect into two components with intensity ratios of 2.7 : 1 and 1.4 : 1, respectively, which were the ratios of the low-temperature peak to the high-temperature peak. Under 〈1 1 0〉 stress, this peak split into three components as an intensity ratio of two lower-temperature peaks to the high-temperature peak was 1.4 : 5 : 1. In addition, we observed the stress-induced alignment of the defect to the configuration corresponding to the low-temperature DLTS peak during the DLTS scan in the temperature range of 65–100 K, for all stress directions. Our results provide the first evidence to connect the electronic level at E c−0.14 eV to the atomic configuration of the Pt–H 2 complex with the C 2v symmetry previously identified by EPR.

Electronic and atomic structure of transition-metal–hydrogen complexes in silicon

Electron paramagnetic resonance investigations on transition-metal-doped silicon, hydrogenated at high temperature in an environment of water vapor, have revealed three transition-metal–hydrogen related paramagnetic centers Si-NL65, Si-NL64, and Si-NL68, respectively, in the samples doped with platinum, gold, and palladium. The spectra, from the sample preparation conditions, and the experimentally observed hyperfine structures of 1 : 3 : 3 : 1–4 : 12 : 12 : 4–1 : 3 : 3 : 1 for the Si-NL65, 1 : 2 : 1–1 : 2 : 1–1 : 2 : 1–1 : 2 : 1 for the Si-NL64, and 1 : 1 for the Si-NL68 spectrum, were identified as complexes of one-platinum–three-hydrogen (Pt–H 3), one-gold–two-hydrogen (Au–H 2), and one-palladium–one-hydrogen (Pd–H 1), respectively. A detailed analysis of the spin-Hamiltonian parameters of the centers, the transition-metal and hydrogen hyperfine interactions, has been carried out providing adequate materials for establishing electronic and microscopic models of the newly observed centers.

Copper–hydrogen complexes in silicon

The deep levels of copper–hydrogen complexes in silicon were investigated by DLTS and MCTS. Copper-doped silicon was hydrogenated by wet chemical etching. Two deep levels at Ec−0.36eV and Ev+0.54eV were attributed to the Cu–H1 complex. A third charge state of this defect might be overlapping with the Cu donor at Ev+0.21eV. The levels at Ec−0.25eV and Ev+0.27eV were assigned to the Cu–H2 defect. The results are compared with former studies on the hydrogen complexing of Au and Ag.

Self-interstitial–hydrogen complexes in silicon

The vibrational properties of interstitial silane (SiH4)i and silyl (SiH3)i molecules in crystalline silicon are calculated using a first-principle, cluster-based, spin-polarized local-density meth ...

Similarities in the electrical properties of transition metal–hydrogen complexes in silicon

We review our recent studies on the reactions of hydrogen with transition-metals (Pd, Pt, Ag, and Au) in crystalline Si. Hydrogen was incorporated into the samples by wet-chemical etching. Deep-level transient spectroscopy (DLTS) on Schottky diodes reveals several transition metal–hydrogen complexes in n- and p-type samples. From DLTS profiling, we are able to estimate the number i of hydrogen atoms in the TM–H i complexes. All complexes with i=1, 2 are electrically active. Striking similarities are found for isoelectronic complexes, e.g. Pt–H 2 and Au–H 1. Transition metal complexes with more than three hydrogen atoms are likely to be electrically passive. All hydrogen related complexes disappear after heat treatments above 600 K for several hours.

The electronic properties of transition metal hydrogen complexes in silicon

The electrical levels of various combinations of transition metal-H n defects in Si are calculated using spin-polarised local density functional cluster theory with an empirical correction. The shifts of these levels with H can be understood through a displacement and splitting of the gap t 2 manifold of states due to the impurity. Passive defects are identified.

The structural properties of transition metal hydrogen complexes in silicon

A first-principles spin-polarised local density functional cluster method is used to explore the structural and vibrational properties of several substitutional transition-metal impurities complexed with hydrogen.

Laplace-transform deep-level transient spectroscopy studies of the G4 gold–hydrogen complex in silicon

We have studied n-type silicon containing gold and gold–hydrogen complexes using high-resolution “Laplace” deep-level transient spectroscopy. This technique has enabled two quite distinct electron emission rates to be observed at temperatures between 240 and 300 K. These are associated with the gold acceptor and the level referred to as G4, which is observed when hydrogen and gold are present in silicon. The gold acceptor has a measured activation energy for electron emission of 558±8 meV, and the G4 state of 542±8 meV. The directly measured electron capture cross section for G4 is determined to be 0.6±0.1 σn(gold acceptor) at 275 K from which it is inferred that the state is acceptor-like.

Electrical Properties of Transition Metal Hydrogen Complexes in Silicon

ABSTRACTA summary is given on the electrical properties of transition-metal hydrogen complexes in silicon. Contrary to the general understanding, hydrogen leads not only to a passivation of deep defect levels but also creates several new levels in the band gap due to electrically active transition-metal complexes. We present detailed data for Pt-H complexes and summarize briefly our results on the transition metals Ti, Co, Ni, Pd, and Ag. The introduction of hydrogen at room temperature by wet chemical etching, followed by specific annealing steps allows us to study the formation of the different complexes. In particular, depth profiles of the defect concentrations give an estimate of the number of hydrogen atoms involved in the complexes. Transition-metals binding up to four hydrogen atoms are identified.

Structural stability and vibrational properties of hydrogen complexes in silicon

The structural stability and vibrational properties of various hydrogen complexes in silicon are investigated using a total energy minimization scheme combined with the empirical tight binding method. The trends of hydrogen-induced relaxations of various complexes are basically in good agreement with the first-principles calculation. The vibrational properties of hydrogen complexes are re-evaluated in this calculational scheme. The authors show that their calculated vibrational frequencies for metastable diatomic complexes are in a range of experimental values observed from various samples. Hence the model can be applied for further dynamical study of light-induced degradation in hydrogenated amorphous silicon.

Formation of extended hydrogen complexes in silicon.

We have examined the nucleation and growth of hydrogen clusters using pseudopotential total-energy calculations. A double-layer {111} H platelet, resulting from clustering of diatomic ${\mathrm{H}}_{2}^{\mathrm{*}}$ complexes, is lower in energy by 0.15 eV per H pair than interstitial ${\mathrm{H}}_{2}$ molecules. This result explains two experimental observations: (1) predominance of Si-H bonding observed in Si containing high H concentrations and (2) the formation of H {111} platelets. The H vibrational frequencies, H-H separations, and other properties of the platelet are in general agreement with experiment.