Structure of clean and arsenic-covered GaN(0 0 0 1) surfaces
Abstract The effect of trace arsenic on the growth and surface structure of GaN(0 0 0 1) has been studied. We find that a partial pressure of only 10 −9  Torr of arsenic during molecular beam epitaxial growth significantly modifies the growth kinetics. Such a small background pressure of arsenic leads to an arsenic-terminated surface displaying a 2×2 reconstruction during growth which is absent for the clean surface. First-principles theoretical calculations show that As-terminated surfaces are energetically more favorable than Ga-terminated surfaces for arsenic pressures of 10 −9  Torr, and structural models for the As-adatom 2×2 reconstruction are presented.
Surface Stability and Growth Kinetics of Compound Semiconductors: An Ab Initio-Based Approach
We review the surface stability and growth kinetics of III-V and III-nitride semiconductors. The theoretical approach used in these studies is based on ab initio calculations and includes gas-phase free energy. With this method, we can investigate the influence of growth conditions, such as partial pressure and temperature, on the surface stability and growth kinetics. First, we examine the feasibility of this approach by comparing calculated surface phase diagrams of GaAs(001) with experimental results. In addition, the Ga diffusion length on GaAs(001) during molecular beam epitaxy is discussed. Next, this approach is systematically applied to the reconstruction, adsorption and incorporation on various nitride semiconductor surfaces. The calculated results for nitride semiconductor surface reconstructions with polar, nonpolar, and semipolar orientations suggest that adlayer reconstructions generally appear on the polar and the semipolar surfaces. However, the stable ideal surface without adsorption is found on the nonpolar surfaces because the ideal surface satisfies the electron counting rule. Finally, the stability of hydrogen and the incorporation mechanisms of Mg and C during metalorganic vapor phase epitaxy are discussed.
Factors Likely to Influence Tort Litigation in the European Union
As the European Union moves towards harmonization in a variety of business, political, and regulatory settings, an opportunity exists to influence the form of tort liability found in these nations. The opportunity should not be missed, with rising concern that U.S. influences will set into motion costly litigiousness, particularly as EU member nations pull back on the level of social programmes available to cover costs typically included in tort claims. To assist policymakers in their deliberations about European Union tort directives, this paper provides discussion of the frequently cited key differences between the U.S. tort systems and what is found in most EU member nations. The discussion is focused on available evidence regarding the influences of these differences as well as important areas of future research. The most important areas seem to be (1) the need to enforce European Law when no defined regulatory body exists for this purpose; (2) the connection between government social programmes and the need for tort liability compensation; (3) and the influence of rules governing payment of legal costs and lawyer fees.