R. I. Dzhioev

Spin diffusion of optically oriented electrons and photon entrainment in n-gallium arsenide

An experimental and theoretical study of spin transport in the n-GaAs semiconductor is reported. Transport of average electron spin from the photoexcited crystal surface is shown to be determined by the spin diffusion process. At the same time the transport of photoexcited carriers takes place primarily through photon entrainment, which transfers nonequilibrium carriers into the bulk of the semiconductor to distances considerably in excess of the electron spin diffusion length. A comparison of the experimental results with theory permits one to determine the average-spin diffusion length and electron-spin relaxation time.

Optical orientation of donor-bound excitons in nanosized InP/InGaP islands

Spin splitting of optically active and inactive excitons in nanosized n-InP/InGaP islands has been revealed. Optically inactive states become manifest in polarized-luminescence spectra as a result of excitons being bound to neutral donors (or of the formation of the trion, a negatively charged exciton) in InP islands. The exchange-splitting energies of the optically active and inactive states have been determined.

Long electron spin memory times in gallium arsenide

Extremely long electron spin memory times in GaAs are reported. It was established by the optical orientation method that the spin relaxation time of electrons localized at shallow donors in n-type gallium arsenide (Nd−NA≈1014 cm−3) is 290±30 ns at a temperature of 4.2 K. The exchange interaction of quasi-free electrons and electrons at donors suppresses the main spin-loss channel for electrons localized at donors—spin relaxation due to the hyperfine interaction with lattice nuclei.

Optical orientation and alignment of excitons in quantum dots

AbstractOptical orientation and alignment of excitons in InAlAs quantum dots in the AlGaAs matrix have been studied both theoretically and experimentally. Experiments performed in a longitudinal magnetic field (Faraday geometry) reveal transformation of optical orientation to alignment and alignment to orientation, which is caused by exchange splitting of the dipole-active exciton doublet and allowed by the quantum-dot low symmetry. A comparison of theory with experiment made with inclusion of the anisotropy of exciton generation and recombination along the

Nuclear Spin relaxation mediated by Fermi-edge electrons in n -type GaAs

[1\bar 10]

Dynamics of carrier recombination in a semiconductor laser structure

and [110] axes permits one to determine the character of dipole distribution in direction for resonant optical transitions in the self-organized quantum-dot ensemble studied.

Study of the Hanle effect with the transverse component of the electron spin orientation in III–V semiconductors

Magnetic interaction between spin-polarized nuclei and optically oriented excitons in a self-organized ensemble of size-quantized InP islands in an InGaP matrix has been studied in a magnetic field in Faraday geometry. The effective magnetic fields generated by polarized nuclei at excitons have been measured. The strengths of these fields were found to be different for active and inactive excitons because of the difference between the excitonic g factors. The heavy-hole g factor has been determined. The active and inactive excitonic states were found to be coupled through cross-relaxation.

Electron Spin Filtering in the GaAs/AlGaAs Interface Space Charge Field

A method based on the optical orientation technique was developed to measure the nuclear-spin lattice relaxation time T1 in semiconductors. It was applied to bulk n-type GaAs, where T1 was measured after switching off the optical excitation in magnetic fields from 400 to 1200 G at low (< 30 K) temperatures. The spin-lattice relaxation of nuclei in the studied sample with nD = 9 × 1016 cm−3 was found to be determined by hyperfine scattering of itinerant electrons (Korringa mechanism) which predicts invariability of T1 with the change in magnetic field and linear dependence of the relaxation rate on temperature. This result extends the experimentally verified applicability of the Korringa relaxation law in degenerate semiconductors, previously studied in strong magnetic fields (several Tesla), to the moderate field range.