H. Duan

THEORETICAL STUDIES ABOUT ADSORPTION ON SILICON SURFACE

In this review paper, we address the important research topic of adsorption on the silicon surface. The deposition of single Si ad-species (adatom and ad-dimer) on the p(2×2) reconstructed Si(100) surface has been simulated by the empirical tight-binding method. Using the clean and defective Si surfaces as the deposition substrates, the deposition energies are mapped out around the clean surface, dimer vacancies, steps and kink structures. The binding sites, saddle points and several possible diffusion paths are obtained from the calculated energy. With further analysis of the deposition and diffusion behaviors, the influences of the surface defects can be found. Then, by adopting the first-principle calculations, the adsorptions of the II-VI group elements on the clean and As-passivated Si(211) substrates have been calculated as the example of adsorption on the high-miller-index Si surface.

The influence of the additional confining potentials on ferromagnetism in III–V digital ferromagnetic heterostructures

The effect of the additional confining potentials on ferromagnetism in III–V digital ferromagnetic heterostructures has been studied by ab initio calculations in combination with pseudopotential plane-wave method. The electronic and magnetic properties are shown as a function of the thickness of AlAs layers in the GaAs∕AlAs digital ferromagnetic heterostructures. It is found that all the structures show ferromagnetic alignment for the most favored configuration and their electronic structures are half metallicity. The exchange coupling constants N0β are estimated by using the spin splitting of the valence band. It is also shown that the charge density and the strong spin polarization are concentrated mostly on the magnetic layers for all structures. Furthermore, the hole distributions are analyzed in terms of their orbital projected density of states. The concentration of confined hole within the magnetic layer increases with increasing the additional potentials, which is responsible for the enhancement o...

ENERGETICS OF VHg-RELATED DEFECTS IN As-DOPED HgCdTe

Arsenic-doped HgCdTe usually exhibits compensated n-type conductivity, which is ambiguously attributed to isolated vacancies (VHg) or arsenic-vacancy complexes (AsHg– VHg and AsHg–2VHg). Our first-principles calculations clarified the correlation of these VHg-related defects with the carrier compensation in As-doped HgCdTe by calculating the defect formation energies, as a function of atomic/electron chemical potentials. Under n-type condition, the lowest formation energy defect is found to be the AsHg donor followed by the VHg acceptor, leading to a compensated n-type material. The arsenic-vacancy complexes are shallow acceptors but their high formation energies render them unlikely to be the compensating candidates. Their large binding energies, however, allow us to predict that the formation of the AsHg–2VHg complex defect will be enhanced under postgrowth annealing treatment, in agreement with the arsenic activation model by Berding et al. [J. Electron. Mater.27, 605 (1998)].

Selective growth of II-VI materials on Si(211): First-principle calculations

Using the First-principle calculation software, the adsorptions of CdTe layers and ZnTe layers on the clean and As-passivated Si(211) substrates are simulated respectively. Based on the computational results, we theoretically interpret the important effects of the As4 passivation during the epitaxial growth: arsenic can saturate part of the dangling bonds and weaken the surface states to make the discrepancy of the substrate surface, which induce the B-face polarity selection automatically. This conclusion can provide further explanations for the successful growth of large area high quality CdTe(211)B layers on the Si(211) surfaces.

FPLAPW investigations of electronic properties of IIB0VI tellurides in the generalized gradient approximation

The electronic properties of zinc-blend ZnTe, CdTe and HgTe are systematically investigated using the FLAPW approach. We find that the essential features of density of states, the influence of d electrons on the band structure, and electronic charge distributions are insensitive to the choice of exchange-correlation potential. Some calculated fundamental parameters show an agreement with experimental and theoretical results.