Publications by Peter Broqvist

Germanium core-level shifts at Ge/GeO2 interfaces through hybrid functionals

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder, Hannu-Pekka Komsa

The Ge core-level shift across the Ge/GeO2 interface is determined within semilocal and hybrid density functional schemes. We first assess the accuracy achieved within these theoretical frameworks by comparing calculated and measured core-level shifts for ...

2012

Band offsets at Ge/GeO2 interfaces: Effect of different interfacial bonding patterns

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder

Using hybrid density functional calculations, we investigate possible origins for the large variation of band offsets measured at Ge/GeO2 interfaces. We consider atomistic model interfaces with both amorphous and crystalline oxides, in which the bond densi ...

Elsevier2011

Charge Trapping in Substoichiometric Germanium Oxide

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder

Electron and hole trapping in substoichiometric germanium oxides are investigated through the use of hybrid density functionals. We consider disordered model structures generated by Monte-Carlo bond switching and by ab initio molecular dynamics (MD). The M ...

2011

Electron density of states at Ge/oxide interfaces due to GeOx formation

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder

An atomistic model of substoichiometric germanium oxide is generated through ab initio molecular dynamics. The resulting structure shows a predominance of threefold coordinated Ge and O atoms. We also generate substoichiometric models through bond-switchin ...

Elsevier2011

Charge transition levels of carbon-, oxygen-, and hydrogen-related defects at the SiC/SiO2 interface through hybrid functionals

Alfredo Pasquarello, Fabien Devynck, Peter Broqvist, Audrius Alkauskas

We calculate charge transition levels of various defects at the SiC/SiO2 interface within a scheme based on hybrid density functionals, which accurately reproduce the involved band gaps and band offsets. The defect levels are first evaluated in bulk models ...

2011

Band offsets at the Ge/GeO2 interface through hybrid density functionals (vol 94, 141911, 2009)

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder

2011

Defect levels of carbon-related defects at the SiC/SiO2 interface from hybrid functionals

Alfredo Pasquarello, Fabien Devynck, Peter Broqvist, Audrius Alkauskas

We investigate carbon single-atom and pair defects at the SiC/SiO2 interface as candidate defects for the density of defect states in the SiC band gap. In order to accurately describe the electronic defect levels with respect to the SiC band edges, we use ...

2011

Defect levels through hybrid density functionals: Insights and applications

Alfredo Pasquarello, Peter Broqvist, Audrius Alkauskas

Hybrid density functional calculations applied to defect charge transition levels are explored in the attempt to overcome the band-gap problem of semilocal density functionals. Charge transition levels of a large set of point defects calculated with semilo ...

2011

Charge transition levels of nitrogen dangling bonds at Si/SiO2 interfaces: A first-principles study

Alfredo Pasquarello, Philipp Dahinden, Peter Broqvist

The defect levels of the nitrogen dangling bond at the Si/SiO2 interface are determined through a density-functional approach. The composition grading at the interface is modeled through crystalline and amorphous models of stoichiometric SiO2, nitrided SiO ...

2010

Formation of substoichiometric GeOx at the Ge-HfO2 interface

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder

The stability of oxygen vacancies across the Ge-HfO2 interface is studied through semilocal and hybrid density-functional calculations. On the semiconductor side, the formation energies are obtained for substoichiometric GeOx of varying x through the use o ...

American Institute of Physics2010

Electronic and structural properties at Ge/GeO2 interfaces: A density-functional investigation

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder

The electronic and structural properties at the Ge/GeO2 interface are addressed through a density-functional simulation scheme, which includes the use of hybrid functionals for achieving defect levels and band gaps comparable to experiment. The present wor ...

Electrochemical Society Inc.2010

Alignment of defect levels and band edges through hybrid functionals: Effect of screening in the exchange term

Alfredo Pasquarello, Peter Broqvist, Hannu-Pekka Komsa

We investigate how various treatments of exact exchange affect defect charge transition levels and band edges in hybrid functional schemes for a variety of systems. We distinguish the effects of long-range vs short-range exchange and of local vs nonlocal e ...

2010

Electron trapping in substoichiometric germanium oxide

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder

Model structures of substoichiometric germanium oxide generated by ab initio molecular dynamics reveal a rich variety of bonding configurations, including threefold coordinated Ge and O atoms which correspond to valence alternation pairs. A sizable fractio ...

American Institute of Physics2010

Defect levels of the Ge dangling bond defect

Alfredo Pasquarello, Peter Broqvist, Audrius Alkauskas

Defect levels of dangling bonds in germanium are calculated through the use of hybrid density functionals. The theoretical approach is first validated through the consideration of the well-characterized defect levels of the dangling bond in silicon, for wh ...

2010

Energy levels of candidate defects at interfaces SiC/SiO2 interfaces

Alfredo Pasquarello, Fabien Devynck, Peter Broqvist, Audrius Alkauskas

We determine energy levels of candidate defects for the high defect density observed just below the SiC conduction band at SiC/SiO 2 interfaces. We address C interstitials and H bridge defects which both show defect levels in the upper part of the SiC band ...

2010

Atomistic model structure of the Ge(100)-GeO2 interface

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder

An atomistic model of the Ge-GeO2 interface has been generated through first-principle methods based on density functional theory. The interface model consists of amorphous GeO2 connected to crystalline Ge through a substoichiometric oxide region showing r ...

2009

Band offsets at the Ge/GeO2 interface through hybrid density functionals

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder

Band offsets of the Ge/GeO2 interface are calculated through a hybrid density functional scheme. We first generate a model of disordered GeO2 through ab initio molecular dynamics to describe the oxide component. For addressing the interface, we then consid ...

AIP American Institute of Physics2009

Alignment of defect energy levels at the Si-SIO2 interface from hybrid density functional calculations

Alfredo Pasquarello, Peter Broqvist, Audrius Alkauskas

2010

First principles investigation of defect energy levels at semiconductor-oxide interfaces: Oxygen vacancies and hydrogen interstitials in the Si-SiO2-HfO2 stack

Alfredo Pasquarello, Peter Broqvist, Audrius Alkauskas

We introduce a scheme for the calculation of band offsets and defect energy levels at semiconductor-oxide interfaces. Our scheme is based on the use of realistic atomistic models of the interface structure and of hybrid functionals for the evaluation of th ...

American Institute of Physics2009

First principles study of substoichiometric germanium oxides

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder

Using density functional calculations, we studied substoichiometric Ge oxides through a series of crystalline models representing the various oxidation states. We evaluated deviations with respect to a bond-energy description in terms of penalty energies f ...

2009