Search

The quantized states for electrons and holes confined in lead-salt semiconductor quantum wells (QW's) grown on (100) and (111) substrates and the corresponding electric-dipole optical transition energies are calculated analytically, within the envelope function approximation and with the Dimmock two-band $\stackrel{\ensuremath{\rightarrow}}{k}\ensuremath{\cdot}\stackrel{\ensuremath{\rightarrow}}{p}$ model for the bulk. The solution takes into account nonparabolicity, anisotropy, and break of valley and spin degeneracy, due to quantum confinement. Transition energies for different PbTe QW's, calculated as a function of temperature and well width, are shown to give a fair description of the observations of the quantum size effect reported in the literature. Limitations of the spherical and of the parabolic approximations to the electronic structure of the lead-salt QW's are made clear and the Rashba spin-orbit term in the effective Hamiltonian is derived.

Atomistic sp3d5s* tight-binding theory of PbSe and PbS nanocrystals is developed. It is demonstrated, that the valley splittings of confined electrons and holes strongly and peculiarly depend on the geometry of a nanocrystal. When the nanocrystal lacks a microscopic center of inversion and has T_d symmetry, the splitting is strongly suppressed as compared to the more symmetric nanocrystals with O_h symmetry, having an inversion center., Comment: 5 pages, 4 figures, 1 table

A formalism for determining energy eigenstates of cylindrical lead salt quantum wires in the multiple-band envelope-function approximation is developed. Electron energy dispersion for quantum wire subbands within the conduction and valence bands is found.