First-Principles Conductance Calculations of Ag-Al Co-Doped ZnO

Based on Density Functional Theory (DFT) first-principles plane-wave ultra-soft pseudo-potential method, we calculated the electronic structure of wurtzite ZnO, Ag-doped ZnO and Ag-Al co-doped ZnO. And we anglicized of energy band structure, electron density of states of Ag-doped and Ag- Al co-doped ZnO crystal. The results indicated: Ag-doped ZnO introduced the deep accepter level in the energy gap, carrier (hole) located near the top of the valence band. And when we add active donor Al to the Ag-Al doped ZnO, the main level moved to low-energy, forming a shallow acceptor level. Meanwhile, the acceptor level got wider, non-localized features got significantly, improving the doping concentration and stability of the system.

Photoluminescence Study of Li-implantation into ZnSe Epitaxial Layers Grown by Molecular Beam Epitaxy

ABSTRACTLithium ion-implantation was performed on ZnSe layers which were grown on GaAs substrates by MBE. Strong photoluminescence emission due to acceptor-bound excitons was observed from samples implanted with lithium doses of up to 1015cm−2 and annealed under optimized conditions for rapid thermal annealing. Lithium implantation results in low damage to the ZnSe as well as the formation of a shallow acceptor level. Thermal degradation of both implanted and unimplanted epilayers caused by the rapid thermal annealing was inviestigated at various annealing temperatures. We find that, under certain annealing conditions, unimplanted samples show greater thermal degradation than lithium implanted samples. The photoluminescence spectrum of an unimplanted sample annealed at 800°C shows considerable degradation; however, a lithium-implanted sample annealed at the same temperature still shows strong luminescence in the excitonic region.

Optical and Electrical Characterizations of AlxGa1−xSb

ABSTRACTThe LPE grown AlxGa1−xSb was investigated by means of TEM, a carrier profiler and PL. The TEM image showed the dissociated 60° dislocations and Lomer-Cottrell sessile dislocation formed by the reaction of two dissociated 60° dislocations on different {111} planes. The EPMA measurement showed that Sb concentrations at the dislocation were lower than the stoichiometric composition. The epi-layer grown at 400°C had a relatively uniform carrier concentration of ∼7×1016cm−3. The PL spectra showed five emission peaks in 0≦×≦0.29. One shallow acceptor level and two native defect levels were introduced to interpret these PL emissions. The shallow acceptor level of Ev+∼30meV may be due to the defect of VGaGaSb. The native defects introduce two levels of EΓ1 - ∼90meV and EL1 - ∼160meV. The defect levels may be related to the complex defect of the Sb vacancy.