Showing papers by "Paolo Giannozzi published in 2002"

Structure and passivation effects of mono- and dihydrogen complexes in GaAsyN(1-y) alloys.

Abstract: In ${\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}}_{y}{\mathrm{N}}_{1\ensuremath{-}y}$, the presence of a few percent of N induces a large reduction of the GaAs band gap that vanishes upon hydrogenation. In the present Letter, the energetics of N-H complexes and their effects on the band structure of the $\mathrm{G}\mathrm{a}\mathrm{A}{\mathrm{s}}_{\mathrm{0.97}}{\mathrm{N}}_{\mathrm{0.03}}$ alloy have been investigated by first-principles density functional methods. We find that monohydrogen $\mathrm{N}\mathrm{\text{\ensuremath{-}}}{\mathrm{H}}^{+}$ and dihydrogen $\mathrm{N}\mathrm{\text{\ensuremath{-}}}{\mathrm{H}}_{2}^{*}$ complexes are formed depending on doping. Moreover, only $\mathrm{N}\mathrm{\text{\ensuremath{-}}}{\mathrm{H}}_{2}^{*}$ complexes account for the neutralization of nitrogen effects. A model is proposed that clarifies the passivation mechanism of nitrogen by H.

Notes on pseudopotential generation

Abstract: When I started to do my first first-principle calculation (that is, my first-principle calculation) with Stefano Baroni on CsI under pressure (1985), it became quickly evident that the available pseudopotentials (PP’s) couldn’t do the job. So we generated our own PP’s. Since that first experience I have generated a large number of PP’s and people keep asking me new PP’s from time to time. I am happy that ”my” PP’s are appreciated and used by other people. However I don’t think that the generation of PP’s is such a hard task that it requires an official (or unofficial) PP wizard to do this. For this reason I want to share here my (little) experience and the (primitive) computer codes I am using.

Defect engineering in III–V ternary alloys: Effects of strain and local charge on the formation of native deep defects

Abstract: The effects of external and internal strains, and of defect charges on the formation of vacancies and antisites in GaAs and In0.5Ga0.5As have been investigated by first principles density functional methods. Present results show that a proper use of strain and defect charges permits the development of a defect engineering of III–V semiconductors. Specifically, they predict that doping may have major effects on the formation of antisites while the formation of vacancies may be favored only by extreme conditions of compressive strain.