Spin dynamics and opto-electronic properties of some novel semiconductor systems

Abstract

A set of problems pertaining to quantum information processing in semiconductors is investigated. Two schemes for implementing electronic qubits in strong and weak three dimensional quantum confinement regimes are studied along with their related electronic properties. Recent experiments motivated us to calculate electronic properties and g factors for nanowhisker quantum dots. These calculations were done using 8 band strain dependent k.p theory on a 3D grid and are in excellent agreement with experiment. It has been observed that the growth conditions cause the nanowhiskers to crystallize in wurtzite(WZ) form instead of their stable-phase zinc-blende bulk structure. Very little is known about the WZ phase of non-nitride III-V semiconductors as they do not naturally occur. We have therefore also predicted the electronic bandstructure and optical properties of nine III-V semiconductors in the WZ phase using transferable empirical pseudopotentials. Apart from quantum dots, the spin of an electron bound to an atomic impurity is an attractive candidate for quantum information processing as they do not suffer from structural uncertainties. This makes spin of an electron bound to a hydrogenic impurity an attractive candidate for a qubit as it possess the biggest radii of any ionic bound states in the solid and is a natural two state system. We have calculated the electric and magnetic field dependent modulation of the g tensor for a single Silicon donor embedded in a GaAs substrate. The spin dynamics of the weakly bound electron exhibits an unusual nonlinear behavior, which is not seen in structures with strong quantum confinement such as quantum dots.