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This study develops a variational approach to calculate the binding energy of a shallow hydrogenic impurity in a n-doped In0.53Ga0.47As/InP single quantum well. Using a proper trial wavefunction, both Schro¨dinger and Poisson equations were solved simultaneously within the effective mass approximation, taking into account finite well barriers, finite temperatures, and different effective masses and dielectric constants along the growth direction. Band bending, screening, and many-body effects were considered and it is found these effects reduce drastically the impurity binding energy and lead to the vanishing of this energy when the 2DEG density reaches a critical value. Our results show that such a vanishing occurs even for very thin quantum wells, contrarily to recent calculations developed for GaAs/AlGaAs quantum wells. [Copyright &y& Elsevier]

Semiconductor–metal transition in a square quantum wire of the GaAs/GaAlAs system is investigated within the effective mass approximation. Vanishing of the donor ionization energy as a function of well width and donor concentration suggests that no transition is possible below a well width of 7 nm. Critical impurity concentrations at which the transition occurs increase with reduction in well width. The effects of Anderson localization and correlation in the Hubbard model are included in a simple way. In general, the critical concentration is one order higher in the square quantum wire system when compared to a quantum well case for lower well widths. When well width is increased it reaches the bulk value in both the cases. The critical concentration is enhanced when a random distribution of impurities is considered. [Copyright &y& Elsevier]

The electronic structures and magnetic features of 3 d transition metals (TM) Cr-, Fe-, Ni-doped InN monolayers are studied by using density functional calculations. The results show that doping these transition metals into InN monolayer can generate magnetic moments, which are primarily distributed in the 3 d atoms and their neighboring N atoms. The Cr- and Fe-doped InN monolayers are magnetic semiconductors, while the Ni-doped InN monolayer shows a half-metallic characteristic. The ferromagnetic (FM) and antiferromagnetic (AFM) couplings of Cr-, Fe-, and Ni-doped InN monolayers are also investigated. It is found that the Cr-doped InN monolayer may exhibit the room-temperature ferromagnetism. Finally, under the biaxial tensile strains, for these magnetically doped InN monolayers, semiconductor-metal phenomenon can be observed. [ABSTRACT FROM AUTHOR]