Structural and optical properties of (In,Ga)As/GaP quantum dots and (GaAsPN/GaPN) diluted-nitride nanolayers coherently grown onto GaP and Si substrates for photonics and photovoltaics applications

San Francisco, California, United StatesInternational audienceLattice-matched GaP-based nanostructures grown on silicon substrates is a highly rewarded route for coherent integration of photonics and high-efficiency photovoltaic devices onto silicon substrates. We report on the structural and optical properties of selected MBE-grown nanostructures on both GaP substrates and GaP/Si pseudo-substrates. As a first stumbling block, the GaP/Si interface growth has been optimised thanks to a complementary set of thorough structural analyses. Photoluminescence and time-resolved photoluminescence studies of self-assembled (In,Ga)As quantum dots grown on GaP substrate demonstrate a proximity of two different types of optical transitions interpreted as a competition between conduction band states in X and Γ valleys. Structural properties and optical studies of GaAsP(N)/GaP(N) quantum wells coherently grown on GaP substrates and GaP/Si pseudo substrates are reported. Our results are found to be suitable for light emission applications in the datacom segment. Then, possible routes are drawn for larger wavelengths applications, in order to address the chip-to-chip and within-a-chip optical interconnects and the optical telecom segments. Finally, results on GaAsPN/GaP heterostructures and diodes, suitable for PV applications are reporte

Mengembangkan pengajaran kejuruan

Judul asli: Developing vocational instrauction5a-85 p. : il.; 22 cm

Mengembangkan Pengajaran Kejuruan

15a + 85 hal.: 21 Cm

Computational investigations and grid refinement study of 3D transient flow in a cylindrical tank using OpenFOAM

The study of physic fluid for a liquid draining inside a tank is easily accessible using numerical simulation. However, numerical simulation is expensive when the liquid draining involves the multi-phase problem. Since an accurate numerical simulation can be obtained if a proper method for error estimation is accomplished, this paper provides systematic assessment of error estimation due to grid convergence error using OpenFOAM. OpenFOAM is an open source CFD-toolbox and it is well-known among the researchers and institutions because of its free applications and ready to use. In this study, three types of grid resolution are used: coarse, medium and fine grids. Grid Convergence Index (GCI) is applied to estimate the error due to the grid sensitivity. A monotonic convergence condition is obtained in this study that shows the grid convergence error has been progressively reduced. The fine grid has the GCI value below 1%. The extrapolated value from Richardson Extrapolation is in the range of the GCI obtained

Effects of temporal frequency towards visual roughness perception by drifted grating stimulation

Previous studies proved that in addition to spatial characteristics function in extracting roughness information, there is potential roughness dependability across changes in the temporal mechanisms of textured surfaces. In the present study, we created temporal coding mechanism by converting fine spatial structure surface into a temporal drifting pattern. We proposed that regular spatial structure of gratings with variation of temporal mechanism have different influence toward roughness perception. Results showed massive individual differences of roughness perception between subjects, suggesting that a combination of spatial and temporal mechanisms accounts for perceptual judgments of roughness. We suggest that visual roughness judgment was determined by spatial in grating stimulation, and improvement is needed in spatial components before temporal coding of visual roughness can be declared