Thermally activated reorientation of di-interstitial defects in silicon

We propose a di-interstitial model for the P6 center commonly observed in ion implanted silicon. The di-interstitial structure and transition paths between different defect orientations can explain the thermally activated transition of the P6 center from low-temperature C1h to room-temperature D2d symmetry. The activation energy for the defect reorientation determined by ab initio calculations is 0.5 eV in agreement with the experiment. Our di-interstitial model establishes a link between point defects and extended defects, di-interstitials providing the nuclei for the growth.Comment: 12 pages, REVTeX, Four figures, submitted to Phys. Rev. Let

Quasiparticle calculations of band offsets at AlN -- GaN interfaces

A first-principle quasiparticle theory in the GW approximation is used to compute valence and conduction band offsets, VBO and CBO, respectively, for hexagonal and cubic AlN -- GaN interfaces. We find type I band offsets that depend on the in-plane lattice constant of the heterostructure, ranging from VBO 1:5 eV for the in-plane lattice constant of a 6H -- SiC (0001) substrate to VBO 1:8 eV for the in-plane lattice constant of a GaN (0001) substrate. This sensitivity may explain the range of experimental results for systems whose in-plane lattice constants could not be directly measured. q 2002 Published by Elsevier Science Ltd