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Peter Broqvist

Cette personne n’est plus à l’EPFL

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Publications associées (35)

Hybrid-functional calculations with plane-wave basis sets: Effect of singularity correction on total energies, energy eigenvalues, and defect energy levels

Alfredo Pasquarello, Peter Broqvist, Audrius Alkauskas

When described through a plane-wave basis set, the inclusion of exact nonlocal exchange in hybrid functionals gives rise to a singularity, which slows down the convergence with the density of sampled k points in reciprocal space. In this work, we investiga ...

2009

Band alignments and defect levels in Si-HfO2 gate stacks: Oxygen vacancy and Fermi-level pinning

Alfredo Pasquarello, Peter Broqvist, Audrius Alkauskas

The determination of band alignments and defect levels is demonstrated for the technologically relevant Si-SiO2-HfO2 gate stack. The proposed scheme, which combines first-principles molecular dynamics for model generation and hybrid density functionals for ...

AIP American Institute of Physics2008

Charge state of the O-2 molecule during silicon oxidation through hybrid functional calculations

Alfredo Pasquarello, Peter Broqvist, Audrius Alkauskas

We study the charge state of the diffusing O-2 molecule during silicon oxidation through hybrid functional calculations. We calculate charge-transition levels of O-2 in bulk SiO2 and use theoretical band offsets to align these levels with respect to the Si ...

2008

Band offsets at semiconductor-oxide interfaces from hybrid density-functional calculations

Alfredo Pasquarello, Fabien Devynck, Peter Broqvist, Audrius Alkauskas

Band offsets at semiconductor-oxide interfaces are determined through a scheme based on hybrid density functionals, which incorporate a fraction alpha of Hartree-Fock exchange. For each bulk component, the fraction alpha is tuned to reproduce the experimen ...

2008

Defect energy levels in density functional calculations: Alignment and band gap problem

Alfredo Pasquarello, Peter Broqvist, Audrius Alkauskas

For materials of varying band gap, we compare energy levels of atomically localized defects calculated within a semilocal and a hybrid density-functional scheme. Since the latter scheme partially relieves the band gap problem, our study describes how calcu ...

2008

Defect levels of dangling bonds in silicon and germanium through hybrid functionals

Alfredo Pasquarello, Peter Broqvist, Audrius Alkauskas

Defect levels of dangling bonds in silicon and germanium are determined within their respective band gaps through the use of hybrid density functionals. To validate our approach, we first considered the dangling bond in silicon finding two well-separated d ...

2008

Charge transition levels of the Ge dangling bond defect at Ge/insulator interfaces

Alfredo Pasquarello, Peter Broqvist, Audrius Alkauskas

We calculate defect levels of dangling bonds in germanium using hybrid density functionals. To validate our approach, we first consider the dangling bond in silicon finding two well-separated defect levels, in excellent correspondence with their experiment ...

2008

Structural and electronic properties of oxygen vacancies in monoclinic HfO2

Alfredo Pasquarello, Peter Broqvist

We study structural and electronic properties of the oxygen vacancy in monoclinic HfO 2 for five different charge states. We use a hybrid density functional to accurately reproduce the experimental band gap. To compare with measured defect levels, we deter ...

2007

Band gaps and dielectric constants of amorphous hafnium silicates: A first-principles investigation

Alfredo Pasquarello, Peter Broqvist

Electronic band gaps and dielectric constants are obtained for amorphous hafnium silicates using first-principles methods. Models of amorphous (HfO2)(x)(SiO2)(1-x) for varying x are generated by ab initio molecular dynamics. The calculations show that the ...

AIP American Institute of Physics2007

Amorphous hafnium silicates: structural, electronic and dielectric properties

Alfredo Pasquarello, Peter Broqvist

Models of amorphous (HfO2)x(SiO2)(1), for varying hafnium, content x are generated by ab initio molecular dynamics. The structural properties are analyzed in terms of pair distribution functions from which typical bond lengths and coordination numbers are ...

2007

Hydrogen in Si(100)-SiO2-HfO2 gate stacks: Relevant charge states and their location

Alfredo Pasquarello, Peter Broqvist

Using a density functional approach, we study the energetics of various charged hydrogen states in the Si(100)-SiO2-HfO2 gate stack. We describe the SiO2-HfO2 transition region through model structures of amorphous hafnium silicate HfxSi1-xO2 with differen ...

AIP American Institute of Physics2007

Migration of oxygen vacancy in HfO2 and across the HfO2/SiO2 interface: A first-principles investigation

Alfredo Pasquarello, Peter Broqvist

Oxygen vacancy migration is studied in monoclinic HfO2 and across its interface with SiO2 through density functional calculations. In HfO2, long-range diffusion shows activation barriers of 2.4 and 0.7 eV for the neutral and doubly positively charged vacan ...

AIP American Institute of Physics2007

First principles investigation of defects at interfaces between silicon and amorphous high-kappa oxides

Alfredo Pasquarello, Peter Broqvist

Experimental characterization is facing severe difficulties in elucidating the nature of defects at interfaces between silicon and amorphous high-kappa oxides. This motivates recourse to first principle simulation approaches based on density functional the ...

2007

Structural and electronic properties of an abrupt 4H-SiC(0001)/SiO2 interface model: Classical molecular dynamics simulations and density functional calculations

Alfredo Pasquarello, Fabien Devynck, Peter Broqvist

Using a density functional approach, we study structural and electronic properties of the 4H(0001)-SiC/SiO2 interface. Through the sequential use of classical and ab initio simulation methods, we generate an abrupt model structure which describes the trans ...

2007

Oxygen vacancy in monoclinic HfO2: A consistent interpretation of trap assisted conduction, direct electron injection, and optical absorption experiments

Alfredo Pasquarello, Peter Broqvist

The authors calculate energy levels associated with the oxygen vacancy in monoclinic HfO2 using a hybrid density functional which accurately reproduces the experimental band gap. The most stable charge states are obtained for varying Fermi level in the HfO ...

AIP American Institute of Physics2006

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