N/P InP homojunction solar cells with an In0.53Ga0.47As contacting layer grown by liquid phase epitaxy

N/P InP homojunction solar cells with an In sub 0.53 Ga sub 0.47 As contacting layer were fabricated by liquid phase epitaxy (LPE). Electron-Beam-Induced-Current (EBIC) measurements were performed on several selected samples. It was found that the background doping level in the base region sometimes results in a deep junction, which greatly affects the cell performance

Theory of resonant spin Hall effect

A biref review is presented on resonant spin Hall effect, where a tiny external electric field induces a saturated spin Hall current in a 2-dimensional electron or hole gas in a perpendicular magnetic field. The phenomenon is attributted to the energy level crossing associated with the spin-orbit coupling and the Zeeman splitting. We summarize recent theoretical development of the effect in various systems and discuss possible experiments to observe the effect.Comment: 5 pages with 1 figure

Complete relativistic equation of state for neutron stars

We construct the equation of state (EOS) in a wide density range for neutron stars using the relativistic mean field theory. The properties of neutron star matter with both uniform and non-uniform distributions are studied consistently. The inclusion of hyperons considerably softens the EOS at high densities. The Thomas-Fermi approximation is used to describe the non-uniform matter, which is composed of a lattice of heavy nuclei. The phase transition from uniform matter to non-uniform matter occurs around $0.06 \rm{fm^{-3}}$, and the free neutrons drip out of nuclei at about $2.4 \times 10^{-4}\ \rm{fm^{-3}}$. We apply the resulting EOS to investigate the neutron star properties such as maximum mass and composition of neutron stars.Comment: 23 pages, REVTeX, 9 ps figures, to appear in Phys. Rev.

Magnetic anisotropy switching in (Ga,Mn)As with increasing hole concentration

We study a possible mechanism of the switching of the magnetic easy axis as a function of hole concentration in (Ga,Mn)As epilayers. In-plane uniaxial magnetic anisotropy along [110] is found to exceed intrinsic cubic magnetocrystalline anisotropy above a hole concentration of p = 1.5 * 10^21 cm^-3 at 4 K. This anisotropy switching can also be realized by post-growth annealing, and the temperature-dependent ac susceptibility is significantly changed with increasing annealing time. On the basis of our recent scenario [Phys. Rev. Lett. 94, 147203 (2005); Phys. Rev. B 73, 155204 (2006).], we deduce that the growth of highly hole-concentrated cluster regions with [110] uniaxial anisotropy is likely the predominant cause of the enhancement in [110] uniaxial anisotropy at the high hole concentration regime. We can clearly rule out anisotropic lattice strain as a possible origin of the switching of the magnetic anisotropy.Comment: 5 pages, 4 figures, to appear in Phys. Rev.

Understanding the roles of urban configuration on spatial heterogeneity and submarket regionalisation of house price pattern in a mix-scale hedonic model: The case of Shanghai, China

Hedonic model is a powerful tool to investigate the important factors featuring cities' house markets globally; but the development of a local regression approach named as 'Mixed Geographically Weighted Regression' (MGWR) has brought a new insight into urban studies in the field of house price modelling with a proper consideration of spatial heterogeneity, which enables urban planners to know valuable local and global information about elements that factor the property value. In this paper, we proposed a two-step framework to understand the spatial heterogeneity and submarket regionalisation via MGWR in a case study of Shanghai. In the first step, a mixed GWR hedonic model is adopted with the incorporation of globally fixed effect and local factors. In this manner, the influence surface of spatial configuration and land use settings on house price patterns are measured by controlling other elements. Compared with the outputs of ordinary least squares (OLS) analysis and purely local model, the results of specified model in this study are more promising, indicating that the spatial heterogeneity of house price is a complex urban system. In the second stage, a data-driven approach is adopted to detect the spatially homogeneous submarkets based on the coefficients of accessibility indices obtained from MGWR instead of the raw data. Comparison of a regular cluster analysis using housing structural information and the prosed approach is conducted. The results suggest that spatial accessibility and function accessibility are key factors in shaping spatially continuous housing sub-markets on multiple scales with other elements. The findings finally reveal that multi-level modelling procedures provide additional and useful insights into the varying relationships between spatial layouts and the housing price distribution and that urban configuration not only affects house price pattern but also influence shifting housing submarkets

P/N InP homojunction solar cells by LPE and MOCVD techniques

P/N InP homojunction solar cells have been prepared by using both liquid phase epitaxy (LPE) and metallorganic chemical vapor deposition (MOCVD) growth techniques. A heavily doped p-In sub 0.53Ga sub 0.47As contacting layer was incorporated into the cell structure to improve the fill factor and to eliminate surface spiking at the front surface. The best conversion efficiencies (total area) obtained under AM 1 illumination are 14.2 percent for a LPE cell and 15.4 percent for a MOCVD cell

Urban function connectivity: Characterisation of functional urban streets with social media check-in data

Social media check-in data, one type of crowdsourcing open data about individual activity-related choices, provides a new perspective to sense people's spatial and temporal preference in urban places. In this paper, through the analysis of the interaction between these scored places on streets, we aim to advance our knowledge of network accessibility with social media check-ins to portray urban structure and related socioeconomic performance more explicitly. By conceptualising an interface graph to reflect the interplay between land-use points and the co-visual paths, we propose a novel framework to characterise the urban streets with land-use connectivity indices that are measured with a new type of place-function signature. A “3-Ds” model is introduced to package three principal dimensions of urban function network, including accessible density, accessible diversity and delivery efficiency, as one integrated index that works towards a comprehensive understanding of function connectivity from each street's midpoints to all reachable land-use points. Streets are further partitioned to the annotated function regions based on function connectivity in different types of active land-use. The results of preliminary studies in the city of Tianjin, China show that the proposed metrics can explicitly describe the inherent function structure and the regions' typology across scales. Compared with space syntax measurements at the same radius for describing the variation of empirically observed house price, the integrated metric can improve the predictability of statistic models sufficiently, and each specified index is confirmed to be statistically significant by controlling other factors. Overall, this research shows that the usage of ubiquitous big social media data can enrich the current description of the urban network system and enhance the predictability of network accessibility on socioeconomic performance