Vibrational properties of impurities in semiconductors

The sites, gap levels, and migration barriers of interstitial H in Si are predicted. The hydrogenation of C‐rich Si results in the formation of H2*(C) and C2H2, in contrast to FZ‐Si where H2 molecules dominate. The fully saturated vacancy (VH4) also forms. This complex is normally stable up to 650 °C. However, in C‐rich Si, VH4 anneals around 550 °C while the VH3HC complex appears. There, C replaces one of the four Si nearest‐neighbors to the vacancy. This implies that VH4 begins to diffuse at 550 °C, and then traps at Cs. This in turn implies that all the VHn complexes (n = 1, 2, 3, 4) are mobile at moderate temperatures. In this paper, we discuss the energetics of H in Si, summarize the key experimental and theoretical results about H interactions in C‐rich Si, and discuss the migration paths and activation energies of the four VHn complexes.

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“…H is a common impurity in Si 1, 2. It is a fast diffuser and easily traps at a range of impurities and defects.…”

Section: Hydrogen In Simentioning

confidence: 99%

Hydrogen in C‐rich Si and the diffusion of vacancy–H complexes

Estreicher

Docaj

Bebek

et al. 2012

Physica Status Solidi (a)

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“…The interest on hydrogen as an impurity in solids and on surfaces is not new, and dates back to several decades. This is in principle one of the simplest impurities, but a deep understanding of its physical properties is complex due to its low mass, and requires the combination of advanced experimental and theoretical methods [6,7]. In addition to its basic interest as an impurity, a relevant characteristic of hydrogen in solids and surfaces is its ability to form complexes and passivate defects, which has been extensively studied in the last thirty years [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Diffusion of hydrogen in graphite: a molecular dynamics simulation

Herrero¹,

Ramı́rez²

2010

J. Phys. D: Appl. Phys.

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Diffusion of atomic and molecular hydrogen in the interstitial space between graphite sheets has been studied by molecular dynamics simulations. Interatomic interactions were modeled by a tight-binding potential fitted to density-functional calculations. Atomic hydrogen is found to be bounded to C atoms, and its diffusion consists in jumping from a C atom to a neighboring one, with an activation energy of about 0.4 eV. Molecular hydrogen is less attached to the host sheets and diffuses faster than isolated H. At temperatures lower than 500 K, H 2 diffuses with an activation energy of 89 meV, whereas at higher T its diffusion is enhanced by longer jumps of the molecule as well as by correlations between successive hops, yielding an effective activation energy of 190 meV.

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“…1 Introduction Density functional theory (DFT) has been proven to be extremely powerful method to study defects in solids. Nowadays, this is a standard tool to investigate their concentration in thermal equilibrium, their interaction with each other, their vibration modes or their hyperfine tensors [1][2][3][4][5]. All these properties are associated with the ground state of the defect.…”

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confidence: 99%

Time‐dependent density functional study on the excitation spectrum of point defects in semiconductors

Gali

2010

Physica Status Solidi (b)

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A common fingerprint of the electrically active point defects in semiconductors is the transition between their localized defect states upon excitation, which may result in characteristic absorption or photoluminescence spectrum. While density functional calculations have been very successful in exploring the ground-state properties like formation energies or hyperfine tensors the density functional theory (DFT), in principle, is not capable of providing reliable excitation spectrum. Timedependent (TD)-DFT, however, addresses this issue which makes possible to study the properties of point defects associated with their excited states. In this paper, we apply the TD-DFT on two characteristic examples: the well-known nitrogen-vacancy defect in diamond and the less known divacancy in silicon carbide. The former defect is a leading candidate in solid state quantum bit applications where detailed knowledge about the excitation spectrum is extremely important. The excitation property of divacancy will be also studied and its relevance in different applications will be discussed. 1 Introduction Density functional theory (DFT) has been proven to be extremely powerful method to study defects in solids. Nowadays, this is a standard tool to investigate their concentration in thermal equilibrium, their interaction with each other, their vibration modes or their hyperfine tensors [1][2][3][4][5]. All these properties are associated with the ground state of the defect. The success of the DFT calculations are based on the well-developed approximate (semi)local functionals [6][7][8][9] that made possible to study relatively large systems at moderate computational cost with a surprisingly good accuracy. We mention here that the commonly used (semi)local functionals suffer from the selfinteraction error [7] which results in the underestimation of the band gap of semiconductors. Nevertheless, for many semiconductors the (semi)local DFT calculations could predict qualitatively well the adiabatic (thermal) ionization energies of defects [1]. However, in pathological cases (semi)local functionals could fail to describe the nature of the defect states correctly due to the self-interaction error. Recent studies have shown [10-14] that non-local hybrid functionals could improve the results at large extent, and

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Vibrational properties of impurities in semiconductors

Cited by 20 publications

References 52 publications

Hydrogen in C‐rich Si and the diffusion of vacancy–H complexes

Hydrogen in C‐rich Si and the diffusion of vacancy–H complexes

Diffusion of hydrogen in graphite: a molecular dynamics simulation

Time‐dependent density functional study on the excitation spectrum of point defects in semiconductors

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