Xia Congxin

Donor Binding Energy in GaAs/Ga1−x AlxAs Quantum Well: the Laser Field and Temperature Effects

Based on the effective-mass approximation theory and variational method, the laser field and temperature effects on the ground-state donor binding energy in the GaAs/Ga1−xAlxAs quantum well (QW) are investigated. Numerical results show that the donor binding energy depends on the impurity position, laser parameter, temperature, Al composition, and well width. The donor binding energy is decreased when the laser field and temperature are increased in the QW for any impurity position and QW parameter case. Moreover, the laser field has an obvious influence on the donor binding energy of impurity located at the vicinity of the QW center. In addition, our results also show that the donor binding energy decreases (or increases) as the well width (or Al composition x) increases in the QW.

Exciton States in Wurtzite InGaN Coupled Quantum Dots

Based on the effective-mass approximation, exciton states confined in wurtzite InxGa1−xN/GaN strained coupled quantum dots (QDs) are investigated, in which the strong built-in electric field effects due to the piezoelectricity and spontaneous polarization are considered. We find that the barrier thickness between the two QDs has a considerable influence on the exciton states and the interband optical transitions. If the barrier thickness is increased, the exciton binding energy is decreased, the emission wavelength is increased, and the electron–hole recombination rate is obviously reduced. Our theoretical results are in qualitative agreement with the experimental measurements.

First-Principles Studies the Lattice Constants and the Electronic Structures of Diluted Magnetic Semiconductors （In,Mn）As

Lattice constants and electronic structures of diluted magnetic semiconductors (In, Mn) As were investigated using the first principles LMTO-ASA band calculation by assuming supercell structures. Three concentrations of the3d impurities were studied (x=1/2, 1/4, 1/8). The effect of varying Mn concentrations on the lattice constants and the electronic structures are shown.

Chemisorption of Fe on Au-passivated Si(001) surface

The chemisorption of one monolayer of Fe atoms on a Au-passivated Si(001) surface is studied by using the self-consistent tight-binding linear muffin-tin orbital method. The Fe adatom chemisorption on an ideal Si(001) surface is also considered for comparison. The chemisorption energy and layer projected density of states for a monolayer of Fe atoms on Au-passivated Si(001) surface are calculated and compared with that of the Fe atoms on an ideal Si(001) surface. The charge transfer is investigated. It is found that the most stable position is at the fourfold hollow site for the adsorbed Fe atoms, which might sit below the Au surface. Therefore there will be a Au–Fe mixed layer at the Fe/Au–Si(100) interface. It is found that the adsorbed Fe atoms cannot sit below the Si surface, indicating that a buffer layer of Au atoms may hinder the intermixing of Fe atoms and Si atoms at the Fe/Au–Si(001) interface effectively, which is in agreement with the experimental results.