Nonlinear Far-Infrared Magnetoabsorption and Optically Detected Magnetoimpurity Effect in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>n</mml:mi></mml:math>-GaAs

Pidgeon, C. R.; Vass, A.; Allan, Graham; Prettl, Wilhelm; Eaves, L.

doi:10.1103/physrevlett.50.1309

Cited by 29 publications

(17 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Studies of such bipolar spin orientation, where both electrons and holes got excited, gave important insights into the mechanisms of spin relaxation. We show below that by combining the circular photogalvanic effect (CPGE) [10] with saturation (bleaching of absorption) spectroscopy [17][18][19][20][21] we are able to probe spin relaxation for monopolar spin orientation. In contrast to the conventional methods of optical spin orientation, in our measurements only one type of charge carriers (electrons or holes) gets spin oriented and is involved in relaxation processes.…”

mentioning

confidence: 99%

Spin-Sensitive Bleaching and Monopolar Spin Orientation in Quantum Wells

et al. 2002

Self Cite

View full text Add to dashboard Cite

Spin-sensitive bleaching of the absorption of far-infrared radiation has been observed in p-type GaAs͞AlGaAs quantum well structures. The absorption of circularly polarized radiation saturates at lower intensities than that of linearly polarized light due to monopolar spin orientation in the first heavy-hole subband. Spin relaxation times of holes in p-type material in the range of tens of ps were derived from the intensity dependence of the absorption. DOI: 10.1103/PhysRevLett.88.057401 PACS numbers: 78.30.Fs, 68.65. -k, 73.50.Mx, 73.50.Pz The spin of electrons and holes in solid state systems is the decisive ingredient for active spintronic devices [1,2] and several schemes of quantum computation [3][4][5]. Especially the combination of ferromagnetic materials with semiconductors seems to be a promising combination for novel functional concepts. Open problems which have to be addressed in this respect involve spin injection into semiconductors, spin relaxation in low-dimensional semiconductor structures, as well as spin detection. Significant progress was made recently: it was shown that spin polarized electrons (or holes) can be injected from magnetic semiconductor materials into semiconductors [6,7]. The presence of spin polarized electrons can be probed by analyzing the Kerr effect [8] or by analyzing the degree of circular polarization of light which gets emitted when polarized electrons recombine with holes. The inverse process, exciting free carriers by circularly polarized light [9], is frequently used to prepare an ensemble of spin polarized carriers. In low-dimensional systems with band splitting in k space due to k-linear terms in the Hamiltonian optical excitation not only leads to a spin polarized ensemble of electrons but also to a current whose sign and magnitude depend on the degree of circular polarization of the incident light (circular photogalvanic effect [10]).For the realization of spintronic devices long spin dephasing times in quantum well (QW) structures are crucially needed. Spin transport must occur without destroying the relevant spin information. Current investigations of the spin lifetime in semiconductors [11][12][13][14][15][16] are based on optical spin orientation by interband excitation. Studies of such bipolar spin orientation, where both electrons and holes got excited, gave important insights into the mechanisms of spin relaxation. We show below that by combining the circular photogalvanic effect (CPGE) [10] with saturation (bleaching of absorption) spectroscopy [17][18][19][20][21] we are able to probe spin relaxation for monopolar spin orientation. In contrast to the conventional methods of optical spin orientation, in our measurements only one type of charge carriers (electrons or holes) gets spin oriented and is involved in relaxation processes. This is achieved by using terahertz radiation which excites intraband or intersubband, but no interband, transitions. Monopolar spin orientation allows us to study spin relaxation without electron-hole interaction and excito...

show abstract

mentioning

confidence: 99%

Spin-Sensitive Bleaching and Monopolar Spin Orientation in Quantum Wells

et al. 2002

Self Cite

View full text Add to dashboard Cite

show abstract

“…The free carrier concentration p, and thus the photoconductive signal AV/V, depends linearly on F for F << Fs and assumes a constant, saturated value, psat = N~i *r--~---in the high intensity limit. This approximation has been 2r~jl used to evaluate resonant impurity photoconductivity in n-GaAs at 4.2 K [3] and was also the basis of interpretation of high power absorption measurements [1,2]. It has been previously shown that at temperatures well below 4.2 K in n-GaAs excited state impact ionization dominates the optically induced free carrier generation.…”

Section: -Imentioning

confidence: 99%

“…(3) gives the typical saturation behaviour aF P :-N~4TlZ 1 + F/Fs (6) which is due to the depleting of the ground state by optical excitations. Here Fs = (2~r~'e/y)-I is the saturation photon flux 1'* density with reyI = 2 ~ T1 + S'T2 the effective relaxation time of optically excited carriers [1,5]. The free carrier concentration p, and thus the photoconductive signal AV/V, depends linearly on F for F << Fs and assumes a constant, saturated value, psat = N~i *r--~---in the high intensity limit.…”

Section: -Imentioning

confidence: 99%

“…In many cases "life times" determined by saturation spectroscopy in extrinsic semiconductors (e.g. [1] and [2]) are artefacts of the underlying model and actually represent mean transition times ignoring the details of the transition kinetics.…”

Section: -Imentioning

confidence: 99%

“…Very detailed measurements have been performed on shallow donor transitions of n-GaAs epitaxial layers in an external magnetic field at low temperatures. As a function of the laser intensity incident on the sample, the absorption coefficient [1,2] and the photoconductive signal due to optical transitions to excited impurity states and cyclotron resonance [3,4,5] have been measured for various magnetic field strengths. The experimental results were analyzed in terms of appropriate rate equation models based on the photothermal free carrier generation process [6].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Nonlinear fir magneto-photoconductivity on quasi-bound Coulomb states of light holes in high purity p-Ge

Jungwirt

Kropf

Prettl

1991

Int J Infrared Milli Waves

Self Cite

View full text Add to dashboard Cite

The far-infrared magneto-photoconductivity due to optical transitions from the acceptor ground state into quasi-bound Coulomb states in p-Ge has been investigated at low temperatures as a function of intensity applying a high-power cw molecular laser. For intensities above about 1 mW/cm 2 the photoconductive signal shows a square root dependence on intensity, which is attributed to nonlinear free carrier capture in the low compensated material. The experimental results are analyzed in terms of a rate equation model yielding the kinetic parameters of the carrier generation-and recombination process involved.

show abstract

Nonlinear THz Spectroscopy of n-Type GaAs

Gaal

Reimann

Woerner

et al. 2007

Ultrafast Phenomena XV

View full text Add to dashboard Cite

In this thesis, the ultrafast dynamics of conduction band electrons in semiconductors are investigated by nonlinear terahertz (THz) spectroscopy. In particular, n-doped gallium arsenide samples with doping concentrations in the range of 10 16 cm −3 to 10 17 cm −3 are studied. A novel source for the generation of intense THz radiation is developed which yields single-cycle THz transients with field amplitudes of more then 400 kV/cm. The THz source uses ultrashort optical laser pulses provided by a Ti:sapphire oscillator. In addition, a two-color THz-pump mid-infrared-probe setup is implemented, which allows for two-dimensional time-resolved experiments in the far-infrared wavelength range. Field ionization of neutral shallow donors in gallium arsenide with intense, ultrashort THz pulses and subsequent coherent radiative recombination of electrons to impurity ground states is observed at room temperature. The superradiant decay of the nonlinear polarization results in the emission of a coherent signal with picosecond lifetimes. Such nonlinear signals, which exhibit a lifetime ten times longer than in the linear regime are observed for the first time. At low temperatures and THz field strengths below 5 kV/cm, Rabi flopping on shallow donor transitions is demonstrated. For the first time, the polar electron-LO phonon interaction is directly measured in the quantum kinetic transport regime. Quasi-instantaneous acceleration of conduction band electrons in the polar gallium arsenide lattice by the electric field of intense THz pulses and subsequent probing of the mid-infrared transmission reveals a modulation of the transmission along the THz-mid-infrared delay coordinate with the frequency of the LO phonon. These modulations directly display the relative phase between the electron motion and its surrounding virtual phonon cloud. Quantum kinetic model calculations fully account for the observed phenomena.

show abstract

Nonlinear Far-Infrared Magnetoabsorption and Optically Detected Magnetoimpurity Effect inn-GaAs

Cited by 29 publications

References 10 publications

Spin-Sensitive Bleaching and Monopolar Spin Orientation in Quantum Wells

Spin-Sensitive Bleaching and Monopolar Spin Orientation in Quantum Wells

Nonlinear fir magneto-photoconductivity on quasi-bound Coulomb states of light holes in high purity p-Ge

Nonlinear THz Spectroscopy of n-Type GaAs

Contact Info

Product

Resources

About