Showing papers by "Paolo Giannozzi published in 1990"
TL;DR: It is found that some degree of cationic mixing must also affect inner planes in the ultrathin regime in order to explain experimental findings.
Abstract: Phonon spectra of ultrathin (GaAs${)}_{\mathrm{n}}$(AlAs${)}_{\mathrm{n}}$ (001) superlattices are studied theoretically using linear-response density-functional techniques. Results are presented for n=1,2,3 superlattices, along with prototype supercell calculations aimed at simulating a completely disordered (alloy) as well as some partially disordered superlattices. Besides interfacial disorder, which modifies the effective confinement length of low-order longitudinal-optic phonons, we find that\char22{}in the ultrathin regime\char22{}some degree of cationic mixing must also affect inner planes in order to explain experimental findings.
65 citations
TL;DR: In this paper, the vibrational properties of GaAs-AlAs alloys have been studied using large supercells to simulate the disorder and ab initio interatomic force constants.
Abstract: The vibrational properties of ${\mathrm{Ga}}_{\mathit{x}}$${\mathrm{Al}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As alloys have been studied using large supercells to simulate the disorder and ab initio interatomic force constants. In agreement with recent experimental evidence, our results indicate that well defined GaAs-like and AlAs-like phonon dispersions exist for any concentration. Besides broadening phonon states with definite wave vector, alloying narrows the optic branches and lowers the longitudinal modes more than the transverse ones, thus reducing the LO-TO splitting. The acoustic bands are instead rather insensitive to the composition.
64 citations
IBM1
TL;DR: In this article, the results of structural optimization and room-temperature molecular dynamics for the singlet states of C 4 and C 10, performed with the Car-Parrinello method, are presented.
37 citations
TL;DR: The results of pseudopotential density-functional supercell calculations of the properties of neutral hydrogen in bulk GaAs were presented in this article, where the equilibrium sites were determined, and the electronic properties for the equilibrium positions were studied.
Abstract: We present the results of pseudopotential density-functional supercell calculations of the properties of neutral hydrogen in bulk GaAs. The equilibrium sites are determined, and the electronic properties for the equilibrium positions are studied. We find that the equilibrium site for unrelaxed GaAs:H is in the low-valence-charge-density region, whereas if the relaxation of the whole lattice is allowed, a shallow equilibrium minimum occurs at an antibonding site near an As ion. The diffusion path is in the high-valence-charge-density region around the As ions with a barrier as low as 0.1 eV. From our results, we suggest that H behaves as a deep acceptor in n-type GaAs and as a deep donor in p-type GaAs, and occupies different positions. Hence passivation of dopants occurs by neutralization.
28 citations
TL;DR: Les energies du mode H de courbure et d'etirement sont estimees pour les sites stables et metastables de l'atome H pour le site stable concordent avec celles des 2 raies d' absorption infra-rouge.
Abstract: Les energies du mode H de courbure et d'etirement sont estimees pour les sites stables et metastables de l'atome H. Leurs valeurs pour le site stable concordent avec celles des 2 raies d'absorption infra-rouge
8 citations
6 citations