Zhang X, Ma S, Zhang Y, Zhang L, Gao W. Nonlocal Edge-Directed Interpolation, in Advances in Multimedia Information Processing - PCM 2009, 10th Pacific Rim Conference on Multimedia, Bangkok, Thailand, December 15-18, 2009 Proceedings.; 2009:1197–1207. 访问链接
Zhang N, Ma S, Gao W. Shape-Based Depth Map Coding, in Fifth International Conference on Intelligent Information Hiding and Multimedia Signal Processing (IIH-MSP 2009), Kyoto, Japan, 12-14 September, 2009, Proceedings.; 2009:316–319. 访问链接
Fluorine ions can be effectively incorporated into AlGaN/GaN high electron mobility transistor (HEMT) structures, enabling the modulation of local potential and carrier density. The physical mechanism of fluorine incorporation in AlGaN/GaN heterojunctions is of fundamental importance to the stability of fluorine ions in AlGaN/GaN HEMTs. In this work, the molecular dynamic (MD) simulation method is used to calculate the potential energies of interstitial and substitutional fluorine atoms in AlGaN/GaN material system. Ziegler-Biersack-Littmark (ZBL), Lindhard-Sorensen (L-S) and Coulomb potential functions are applied in the MD simulation. The geometric lattice structures, spontaneous and piezoelectric polarizations, and temperature dependence are also included in the simulation. The activation energies associated with interstitial-substitutional and interstitial-interstitial diffusions are obtained. It is revealed that the fluorine ions are most likely located at the substitutional group-III cation sites S(III) and the diffusion of fluorine ions should be dominated by S(III)-interstitial process which exhibits an activation energy of 1.1 eV in Al(0.25)Ga(0.75)N and 1.4 eV in GaN in the presence of group-III vacancies. It is expected that the removal of group-III vacancies can significantly suppress the fluorine diffusion, which in turn, leads to excellent fluorine stability in III-nitride materials. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
The diffusion properties of fluorine ions in GaN are investigated by means of Time-of-Flight secondary ion mass spectroscopy. Instead of incorporating fluorine ions close to the sample surface by plasma, fluorine ion implantation with an energy of 180 keV is utilized to implant fluorine ions deep into the GaN bulk, preventing the surface effects from affecting the data analysis. It is found that the diffusion of fluorine-ions in GaN is a dynamic process, featuring a two-step process. A defect-assisted diffusion model is proposed to account for the experimental observations. Fluorine ions tend to occupy Ga vacancies induced by fluorine ion implantation and diffuse to vacancy rich regions. The fluorine ions become stable after continuous vacancy chains are significantly reduced or removed by thermal annealing. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
A hybrid molecular dynamics (MD)/kinetic Monte Carlo (KMC) model is developed for atomistic modeling of fluorine ion implantation and diffusion in AlGaN/GaN heterostructures. The MD simulation reveals the F distribution profiles and the corresponding defect profiles, and most importantly, the potential energies of fluorine ions in the III-nitride material system. Using the results from the MD simulation, the diffusion process is simulated with KMC method, and the modeling results are validated by the secondary-ion-mass-spectrum (SIMS) measurement. The surface effect on the fluorine's stability and its improvement by passivation are also successfully modeled.