This study is focused on the modulation response of resonant-cavity light-emitting diodes (RCLEDs). Platinum (Pt) atoms are diffused into the 660nm RCLED epitaxial layers to increase the concentration of recombination centers and to improve the modulation speed. The RCLED has an AlInGaP multi-quantum-well active layer which was embedded into AlGaAs-distributed Bragg reflectors to form a one-wavelength (1-λ) optical resonator. Afterwards, the deep-level Pt impurity was diffused into the RCLED and an improved average rise time, from 18.07to12.21ns, was obtained. The corresponding modulation frequency can be increased from 19.54to30.21MHz.
The precipitation of arsenic in superlattice structures of alternately undoped and [Be]=2.4×1019 cm−3 doped GaAs grown at low temperatures has been studied using transmission electron microscopy. Novel precipitate microstructures were observed in annealed samples, including preferential accumulation of precipitates toward each interface of Be-doped GaAs and the following grown undoped GaAs. Specifically, after 800 °C annealing, the precipitates are totally confined in Be-doped regions, forming two-dimensional dot arrays near the aforementioned interfaces. Data are also presented to show that the heavily Be-doped GaAs has a smaller lattice constant than the undoped GaAs. A strain-induced mechanism was proposed to account for the segregation of As clusters.
The precipitation of arsenic in annealed Be delta-doped GaAs grown by low-temperature molecular-beam epitaxy has been studied using transmission electron microscopy. It was found that the planes doped with [Be]=1.0×1014 cm−2 always accumulate As precipitates, while the planes doped with [Be]=1×1013 cm−2 tend to deplete As precipitates. In contrast, the planes doped with [Be]=3 and 2×1013 cm−2 exhibit a weak accumulation property when annealed at 700 °C, but a depletion property when annealed 800 °C. The existence of twins and/or precipitates around the [Be]=1.0×1014 cm−2 doped planes found in the as-grown sample suggests a strain-induced mechanism to account for the As precipitates accumulation on these planes.
equilibrium between ionization and recombination is obtained, and the interpretation of diagnostic observations and the The available literature on electron impact ionization of ions of charge development of realistic models of these plasmas require an + 3 or greater is reviewed. Several easily used formulae are presented the classical result, the Lotz formula, and a scaled Coulomb-Born understanding Of both ionization and recombination. k l e cprescription. The available experimental cross-sections, which now tronic recombination proceeds through excited states similar include a few good quality crossed-beams measurements, are compared to those involved in excitation-autoionization. While the states with the cross-sections obtained from the formulae and, where available, involved are not exactly the same, the excitation process is with true Coulomb-Born calculations. The Lotz formula is overall found important in both the ionization and recombination events to be closest to the experimental results. However, this result is fortuitous since much of the experimental data are found to contain measurable w h~h control ionization contribution from the excitation-autoionization process not included There are additional constraints for relevance to fusion in any of the fm-"e. It appears to be more important to include plasmas. Heavy impurity atoms cannot be tolerated in tokamakestimates of the excitation-autoionization contribution to ionization type plasmas because their ions radiate energy too efficiently, It cross-sections than to improve the models of the direct ionization process. now seems unlikely that atoms with electronic configurations in plasmas.
The structure relationship of the As precipitates found in post-annealed Si δ-doped GaAs layers grown by low-temperature molecular beam epitaxy is elucidated by transmission electron microscopy (TEM). There are six extra spots around the diffraction pattern of GaAs for a sample annealed at 700° C. The As precipitates and GaAs matrix are found to be semicoherent with the hexagonal [-1-21] As parallel to the cubic [110] GaAs. Because of the different lattice constants and Bravias lattices between GaAs and As precipitates, these extra spots are formed by double-diffraction effects. The high-resolution TEM images show two types of Moiré fringes. One is the parallel Moiré pattern and the other is the rotation Moiré pattern. The relative positions of the extra spots in the diffraction pattern correspond to the orientation and spacing of Moiré fringes.
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