Carrier lifetime and spin relaxation time study for electrical spin injection into GaAs (original) (raw)

Room-temperature spin injection and spin loss across a GaNAs/GaAs interface

Applied Physics Letters, 2011

Recently discovered effect of spin-filtering and spin amplification in GaNAs enables us to reliably obtain detailed information on the degree of spin loss during optical spin injection across a semiconductor heterointerface at room temperature. Spin polarization of electrons injected from GaAs into GaNAs is found to be less than half of what is generated in GaNAs by optical orientation. We show that the observed reduced spin injection efficiency is not only due to spin relaxation in GaAs, but more importantly due to spin loss across the interface due to structural inversion asymmetry and probably also interfacial point defects.

Spin lifetimes of electrons injected into GaAs and GaN

Applied Physics Letters, 2003

The spin relaxation time of electrons in GaAs and GaN are determined with a model that includes momentum scattering by phonons and ionized impurities, and spin scattering by the Elliot-Yafet, D'yakonov-Perel, and Bir-Aronov-Pikus mechanisms. Accurate bands generated using a longrange tight-binding Hamiltonian obtained from empirical pseudopotentials are used. The inferred temperature-dependence of the spin relaxation lifetime agrees well with measured values in GaAs. We further show that the spin lifetimes decrease rapidly with injected electrons energy and reach a local maximum at the longitudinal optical phonon energy. Our calculation predicts that electron spin lifetime in pure GaN is about 3 orders of magnitude longer than in GaAs at all temperatures, primarily as a result of the lower spin-orbit interaction and higher conduction band density of states.

Relaxation of electron spin during high-field transport in GaAs bulk

Journal of Statistical Mechanics: Theory and Experiment, 2010

A semiclassical Monte Carlo approach is adopted to study the multivalley spin depolarization of drifting electrons in a doped n-type GaAs bulk semiconductor, in a wide range of lattice temperature (40 K < T L < 300 K) and doping density (10 13 cm −3 < n < 10 16 cm −3 ). The decay of the initial non-equilibrium spin polarization of the conduction electrons is investigated as a function of the amplitude of the driving static electric field, ranging between 0.1 and 6 kV cm −1 , by considering the spin dynamics of electrons in both the Γ-valley and the upper valleys of the semiconductor. Doping density considerably affects spin relaxation at low temperature and weak intensity of the driving electric field. At high values of the electric field, the strong spin-orbit coupling of electrons in the L-valleys significantly reduces the average spin polarization lifetime, but, unexpectedly, for field amplitudes greater than 2.5 kV cm −1 , the spin lifetime increases with the lattice temperature. Our numerical findings are validated by a good agreement with the available experimental results and with calculations recently obtained by a different theoretical approach.

Hot carrier effects on lateral electron spin diffusion inn-type GaAs

Physical Review B, 2013

We report on spatially resolved two-color pump-probe Hanle-magneto-optical Kerr effect studies of lowtemperature electron spin diffusion in bulk n-type GaAs (n D = 1.4 × 10 16 cm −3). The influence of the lattice temperature on electron spin diffusion is investigated and it is shown that simple drift-diffusion models do not describe the spin diffusion for above-band-gap optical spin injection correctly. Variation of lattice temperature and excitation energy allow us to trace this discrepancy to the influence of the pump-induced local overheating of the electron system with respect to the lattice which persists over length scales comparable to the spin diffusion length. Consideration of this hot carrier effect is crucial for a reliable extraction of spin propagation parameters from optical experiments.

Optical and electrical spin injection and spin transport in hybrid Fe/GaAs devices

Journal of Applied Physics, 2007

We discuss methods for imaging the nonequilibrium spin polarization of electrons in Fe/GaAs spin transport devices. Both optically-and electrically-injected spin distributions are studied by scanning magneto-optical Kerr rotation microscopy. Related methods are used to demonstrate electrical spin detection of optically-injected spin polarized currents. Dynamical properties of spin transport are inferred from studies based on the Hanle effect, and the influence of strain on spin transport data in these devices is discussed.

Spin lifetime in high quality InSb epitaxial layers grown on GaAs

Journal of Applied Physics, 2007

The spin relaxation in undoped InSb films grown on GaAs has been investigated in the temperature range from 77to290K. Two distinct lifetime values have been extracted, 1 and 2.5ps, dependent on film thickness. Comparison of this data with a multilayer transport analysis of the films suggests that the longer time (∼2.5ps at 290K) is associated with the central intrinsic region of the film, while the shorter time (∼1ps) is related to the highly dislocated accumulation region at the film-substrate interface. Whereas previous work on InAs films grown on GaAs showed that the native surface defect resulted in an additional charge accumulation layer with high conductivity but very short spin lifetime, in InSb layers the surface states introduce a depletion region. We infer that InSb could be a more attractive candidate for spintronic applications than InAs.

Optical investigation of electrical spin injection into semiconductors

Physical Review B, 2003

In this paper one can find a detailed description of the research performed by author during his stay at IMEC (Belgium). It deals with the experimental verification of the highly coherent electron spin transport across ferromagnetic metal / semiconductor interface at low and room temperatures.

Low-temperature spin relaxation in n-type GaAs

Physical Review B, 2002

Low-temperature electron-spin relaxation is studied by the optical orientation method in bulk n-GaAs with donor concentrations from 10 14 cm Ϫ3 to 5ϫ10 17 cm Ϫ3 . A peculiarity related to the metal-to-insulator transition is observed in the dependence of the spin lifetime on doping near n D ϭ2ϫ10 16 cm Ϫ3 . In the metallic phase, spin relaxation is governed by the Dyakonov-Perel mechanism, while in the insulator phase it is due to anisotropic exchange interaction and hyperfine interaction