David Huy Trinh

Dynamics of bound excitons versus thickness in freestanding GaN wafers grown by halide vapor phase epitaxy

The bound exciton recombination properties in freestanding GaN layers of various thicknesses grown by halide vapor phase epitaxy have been characterized by time-resolved spectroscopy. Improvement of the donor bound exciton (D0X) lifetime was observed with increasing GaN layer thickness up to ∼400μm, while for thicker layers the recombination time of D0X shows a tendency to saturate. The thickness-dependent behavior of the D0X decay can be understood in terms of competition between two nonradiative mechanisms: one of which is connected to structural defects, and consequently more important for thinner layers, while for layers with thickness above 400μm with low structural defect density the recombination time is limited by point defects such as impurities and vacancies.

Influence of the normalized ion flux on the constitution of alumina films deposited by plasma-assisted chemical vapor deposition

Alumina thin films were deposited onto tempered hot working steel substrates from an AlCl3–O2–Ar–H2 gas mixture by plasma-assisted chemical vapor deposition. The normalized ion flux was varied during deposition through changes in precursor content while keeping the cathode voltage and the total pressure constant. As the precursor content in the total gas mixture was increased from 0.8% to 5.8%, the deposition rate increased 12-fold, while the normalized ion flux decreased by approximately 90%. The constitution, morphology, impurity incorporation, and the elastic properties of the alumina thin films were found to depend on the normalized ion flux. These changes in structure, composition, and properties induced by normalized ion flux may be understood by considering mechanisms related to surface and bulk diffusion.

Experiments and modeling of dual reactive magnetron sputtering using two reactive gases

Reactive sputtering from two elemental targets, aluminum and zirconium, with the addition of two reactive gases, oxygen and nitrogen, is studied experimentally as well as theoretically. The complex ...