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We apply Clifford algebra to investigate 2D electron spin reflection off and transmission through a stepped discontinuity of physical parameters in semiconducting quantum well. The discontinuity may be due to change of spin-orbit interaction constants, effective masses, or electrostatic potential. In the paper the posed problem has been solved exactly. It is shown that the reflected electronic beam has identical spin polarization as the incident one. However, the transmitted beam suffers spin flipping and in general case consists of a mixture of up and down spin states. Optimal conditions for total reversion of 2D electron spin polarization are found. Special attention is paid to correct boundary conditions in the presence of spin-orbit interaction. A simple formula that connects spin polarization of the transmitted beam and SO interaction constants is presented. Keywords: Clifford algebra, geometric algebra, semiconductors, spintronics, spin polarization, spin flipping, quantum well

The scattering of valence band hole spin by acoustical and optical phonons due to deformation potential interaction is considered. Six-band deformation potential matrix, which takes into account doubly degenerate heavy-mass, light-mass, and split-off energy bands, is used to evaluate the matrix elements for spin conserving and flipping transitions. The concept of the spin surface was addressed to define the initial and final states of the hole spin. It was found that, in agreement with experiment, the spin conserving and flipping transitions are of comparable magnitude in both intravalence and intervalence band scattering mediated by acoustical as well as optical phonons.

Spin properties of holes in the wurtzite semiconductors, when the hole with a given wave vector ballistically propagates in either heavy-, light-mass or crystal-field split-off band, are considered. Analytical solutions for an averaged hole spin are found for two important cases, when the hole wave vector is parallel and perpendicular to the hexagonal axis. Shapes of the spin surfaces are presented for these cases. It is shown that the surfaces, in general, are spheroids. However, depending on the wave vector magnitude and valence band parameters, the surfaces may also be spheres or line-shaped. The properties of the spin surfaces are illustrated for parameters of the wurtzite GaN, where the crystal field dominates in the splitting of the valence band.

We present the results of time-resolved photoluminescence (TRPL) and optically detected microwave resonance (ODMR) spectroscopy investigations of semiconductor quantum dots and quantum wells. The ODMR spectra of InAs/GaAs QDs were detected via modulation of the total intensity of the QDs emission induced by 95 GHz microwave excitation and exciton fine structure was studied. Very long life times (up to 10 ns) of photoexcited carriers were observed in this system using TRPL at low temperatures and excitation intensities promising higher responsitivity of such QDs for quantum dot infrared photodetector development. The effects of proton and alpha particles irradiation on carrier dynamics were investigated on different InGaAs/GaAs, InAlAs/AlGaAs and GaAs/AlGaAs QD and QW systems. The obtained results demonstrated that carrier lifetimes in the QDs are much less affected by proton irradiation than that in QWs. A strong influence of irradiation on the PL intensity was observed in multiple QWs after high-energy alpha particles irradiation.

Undoped multiple quantum well (MQW) samples grown by the molecular beam epitaxy method were irradiated by 5.15 MeV energy alpha particles. A strong influence of irradiation on the photoluminescence (PL) intensity was observed in these nearly intrinsic samples: the PL intensity at liquid nitrogen and room temperatures decreased by more than two orders of magnitude at alpha particle fluence of 10(exp 11) cm(exp -2). The dependence of the PL intensity on irradiation dose is described by a rate equation model that takes into account the generation of nonradiative point centers in barriers and wells of the MQW structure during irradiation.

Spin precession of a ballistic-hole when external magnetic field is absent and when the hole freely propagates in either heavy- or light-mass band is considered. The spin precession is due to linear in wave vector terms in the Luttinger-Kohn Hamiltonian. It was found that in contrast to conduction-band the valence band spin precession orbits are not circular. They are either ellipses or lines for light- and heavy-holes, respectively. The results of the paper can be applied to describe hole spin-dynamics in A3B5 compounds, for example, in simulation of spin-FETs by Monte Carlo method.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.