Narrow Results

Using a variational approach, we have calculated the impurity position dependence of the photoionizaton cross-section and the binding energy for a hydrogenic donor impurity in a quantum well wire in the presence of the electric and magnetic field as a function of the photon energy. Our calculations have revealed the dependence of the photoionizaton cross-section and the impurity binding on the applied electric and magnetic field, and the impurity position.

We have used silicon impurities in an aluminum arsenide barrier to probe an adjacent two-dimensional electron gas (2DEG). A single impurity acts as a local spectrometer and scans the local density of states of the 2DEG. Magnetotransport experiments have been performed at low temperature with a magnetic field B applied along the direction of the current. Current–voltage characteristics strongly depend on B and reveal the formation of Landau levels (LLs).

Dipole transition moment (DTM) of a hydrogenic donor in a spherical quantum dot of GaAs–Ga_1-xAl_xAs system with finite barrier confinement is obtained. The variational approach within the effective mass approximation is used as the framework for the calculation of donor ionization energy for a few excited states in quantum dot. Calculations of the DTM of an on-center shallow donor hydrogenic impurity in a GaAs quantum dot under hydrostatic pressure are presented. A linear increase in the DTM has been observed, when the dot radius increases from 2 nm to 100 nm. The important conclusions arrived at are (i) ionization energy increases and attains a maximum value occurring for a dot radius of 5 nm, after which the ionization energy decreases gradually as the dot radius increases; (ii) ionization energy for the ground state (1s) is high compared to the excited states (1p and 1d states) and (iii) a linear trend for 1p–1d transition is obtained.

An impact of positions of Te atoms substituting W atoms in two-dimensional WS₂/WSe₂ heterostructures on their electronic properties is investigated by theoretical simulation. The substitution of W by Te tends to reduce the energy band gap and can lead to metallic properties depending on the impurity position and concentration.