Search

Abstract: A detailed computational study is carried out to investigate the effects of Grashof (Gr) and Reynolds (Re) numbers on the three-dimensional (3-D) flow structures and heat transfer characteristics in a horizontal chemical vapor deposition (CVD) reactor with a circular heated disk which simulates a 12-inch wafer. The Grashof number is varied from 8.13×104 to 813 and the Reynolds number is from 100 to 25. For the range of parameters studied, both the transverse (return flow) and longitudinal rolls are observed to appear in 3-D. Computed flow structures and heat flux distributions suggest that for constant Grashof number condition the size and location of longitudinal rolls have direct impact on the homogeneity of deposition, while the size and location of transverse rolls have a minor effect on the heat flux and hence on the deposition rate. In addition, the effect of Reynolds number on the averaged heat flux is negligible under a fixed Grashof number condition. The buoyancy-to-inertia ratio is found to play an effective role in retarding the formation of transverse and longitudinal rolls. [Copyright &y& Elsevier]

Phonon-drag imaging has been used to study the electron-phonon interaction in a low-mobility n-type gallium nitride (GaN) epilayer grown by molecular beam epitaxy on sapphire. Currents up to j=4.7x10[sup 3] A/m[sup 2] were induced by transverse acoustic phonon drag of electrons in this structure. Such currents are much bigger than predicted by the conventional theory of electron-phonon interaction. We explain this difference by the fact that, in low-mobility GaN, the 2k[sub F] cutoff for electron-phonon transitions is relaxed. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]