Study of the optical and structural properties of multi quantum well structures grown on high-index surfaces
The MOVPE overgrowth of high [01@?1]-oriented ridges confined at sides by facets related to {n11} crystallographic planes is reported. We studied the influence of the side tilt on the thickness of the AlGaAs and GaAs epitaxial layers grown under the condition of the kinetic growth mode. The multi quantum well (MQW) structures were prepared on the sides of ridges tilted at 54.7^o, 45^o and 30^o to (100). The sidewall surface morphologies before and after epitaxial growth were evaluated and compared. We observed no tendency towards planarization towards a neighbouring high-index crystallographic plane, such as (211) and (311). We also showed that the quantum wells of the MQW structure make a smooth transition over the edge between the top surface and the facet as both AlGaAs and GaAs grew at similar rates on the surfaces.
Investigation of the GaAs-pyramids overgrowth using MOCVD
Abstract In this work, the epitaxial overgrowth of high and smooth GaAs mesas is presented. GaAs mesas of sidewall slope 35°, 40°, 45°, and 55° were first prepared by wet-chemical etching in H 3 PO 4 , H 2 O 2 , H 2 O based solution. Then the metallorganic chemical vapour deposition was used for the mesas overgrowth. The influence of the growth conditions—temperature, V/III ratio, and growth rate—on the mesa-sidewall morphology was studied using optical microscopy, scanning electron microscopy and atomic force microscopy. We show that the sidewall quality is very high for all mesa slopes for growth rate 0.6 μm/h, V/III ratio 383, and growth temperature 640°C. Grown structures reveal strong tendency for faceting into {1 1 0} crystallographic planes.
Numerical Simulation of Induction Heating Process of Continuous Casting Slab
Compared with traditional blazing furnace, the Continuous Casting-Direct Rolling is an advanced manufacturing steel technology, which can reduce energy waste, decrease pollution and enhance efficiency. The characteristics of steels during induction heating are complex, the change of material properties with temperature makes exact analysis methods very difficult to implement. Therefore, a powerful computer aided numerical tool (i.e., finite difference analysis) is selected to numerically model the induction heating process in this paper. The mathematic model coupling with electromagnetic field and thermal field was established, and it was solved by finite difference method (FDM), thus the slab temperature distribution and its variation with time were obtained, and the characteristics in whole induction heating process were studied. To validate the program feasible, the results were evaluated and compared with experiment results, which showed that the simulation results are reliable and effective. The skin effect in heating process from the two results was studied and demonstrated, the temperature change caused by different parameters such as the induced power intensity and the corner radian were also presented, which indicate that the slab temperature can be heated uniformly through adjusting these parameters, thus the continuous casting slab can meet the rolling requirement.