Initial thermalization of photoexcited carriers in GaAs studied by femtosecond luminescence spectroscopy

Elsaesser, Thomas; Shah, Jagdeep; Rota, L.; Lugli, Paolo

doi:10.1103/physrevlett.66.1757

Cited by 299 publications

(139 citation statements)

References 18 publications

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“…11 Also, assuming that at point a in I(V), the mean electric field around the constriction is given by E a ϷV a /l eff , we can use the relation k m ϭeE a s /បϭ0.96ϫ10 8 m Ϫ1 to obtain an estimate for the scattering time, s , from our measurements. This gives s Ϸ0.2 ps, which is consistent with other values reported in the literature using optical excitation techniques, 12,13 and a value of lϷv m Ϸ13 nm. We can gain further insight into the role of the inflection point at ␣ on the I(V) characteristics by calculating the effect of changing the QW width, L QW , on the dispersion of the lowest-energy hole subband.…”

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confidence: 80%

Nonlinear hole transport through a submicron-size channel

Makarovsky

Neumann

Martin

et al. 2003

Applied Physics Letters

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We investigate hole transport through a submicron-size channel fabricated from a modulation-doped p-type GaAs/͑AlGa͒As single-quantum-well heterostructure. The intense electric field in the channel accelerates the holes beyond the inflection point of the lowest energy subband dispersion curve. This leads to current saturation and negative differential conduction effects in the currentvoltage characteristics. © 2003 American Institute of Physics. ͓DOI: 10.1063/1.1543643͔The energy-wave vector, (k), dispersion curves of holes in a quantum well ͑QW͒ are highly nonparabolic due to the admixing of the heavy-hole ͑HH͒ and light-hole ͑LH͒ subbands by spin-orbit interaction.1,2 In particular, the lowest-energy subband ͑HH1͒ has an inflection point in (k), corresponding to a maximum hole velocity, phenomenologically similar to that found for Bloch electrons in superlattices.3 At energies above this point, the subband has a region with negative effective mass ͑NEM͒. It has been proposed that this property can be exploited to develop a class of high-frequency ͓terahertz ͑THz͔͒ generators and detectors in which ballistic holes are accelerated by an intense electric field to their peak velocity in a submicron high-field device. 4 Alternatively, optical excitation of holes followed by radiative intersubband relaxation could be used as a source of THz radiation. 5In this letter, we investigate hot-hole transport through a submicron-size channel fabricated from a modulation-doped p-type GaAs/͑AlGa͒As single QW heterostructure. Studies of hole transport through narrow constrictions have been reported previously and have shown quantized conductance effects. 6 Here, we show that holes can be accelerated up to and beyond the inflection point in the highly nonparabolic HH1 subband of the QW, thus leading to current saturation and negative differential conduction effects in the currentvoltage characteristics.The GaAs/Al 0.3 Ga 0.7 As heterostructure was grown by molecular beam epitaxy on a semi-insulating ͑SI͒, ͑311͒A-oriented GaAs substrate. It consists of a 15 nm wide QW, modulation-doped with Si acceptors. Transport measurements in standard Hall bars at Tϭ1.2 K gave a hole mobility ϭ50 m 2 /V s and a sheet density pϭ2.1ϫ10 15 m Ϫ2 for the two-dimensional hole gas ͑2DHG͒.Using electron beam lithography, the layer was processed into a four-terminal device in which holes can flow through a narrow constriction between contacts 1 and 3 or 2 and 4 ͑see Fig. 1͒. The constriction is formed by dry etching the heterostructure down to the SI substrate. The contact pads allow us to make four-terminal measurements so that the effect of contact resistances can be eliminated. In the current-voltage characteristic, I(V), shown in Fig. 2͑a͒, the voltage V comprises the potential drop across the short and narrow constriction and across the larger low-resistance tapered areas between the constriction and the contact pads. We studied several structures with different geometrical constriction widths, w, and/or pitch angles, ⌰ ͑see Fig. 1͒. Here, we fo...

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confidence: 80%

Nonlinear hole transport through a submicron-size channel

Makarovsky

Neumann

Martin

et al. 2003

Applied Physics Letters

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“…A homogeneous linewidth of 7 meV is equivalent to T 2 ϭ190 fs. Above the excitonic transition, faster dephasing times ͑less than 100 fs͒ of band-to-band transitions have been measured both in bulk and QW's, [15][16][17] strongly influenced by carrier-carrier scattering, even though phonon emission gives additional dephasing. Dephasing times in bulk and QW diode lasers are generally considered to be fast ͑30-70 fs͒ due to carrier-carrier scattering, as also shown by the fast spectral-hole burning recovery time from pump-probe measurements in semiconductor optical amplifiers.…”

Section: ͑4͒mentioning

confidence: 99%

Dephasing in InAs/GaAs quantum dots

et al. 1999

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“…Both Faraday and Kerr magneto-optical effects 1,3,6 are indeed well suited to study the spin dynamics in both a broad spectral and thermal range, as well as in a thermal range. In particular, they provide a good alternative to the well-known photoluminescence techniques 5 at wavelengths or temperatures for which there is hardly any measurable luminescence. For the study of thick, nontransparent samples such as those described in this paper, the Kerr effect in the reflection geometry is preferred.…”

Section: Introductionmentioning

confidence: 99%

“…The ultrafast dynamics of spins in metallic ferromagnets as well as in magnetic and even nonmagnetic semiconductors [1][2][3][4][5][6] has attracted intense research activity in recent years. In the case of semiconducting materials such as gallium arsenide ͑GaAs͒, essentially low-dimensional systems have been investigated, mostly at low temperature.…”

Section: Introductionmentioning

confidence: 99%

Room-temperature ultrafast carrier and spin dynamics in GaAs probed by the photoinduced magneto-optical Kerr effect

et al. 2001

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The picosecond and subpicosecond dynamics of spins in intrinsic and n-doped GaAs is investigated at room temperature using the time-resolved, pump and probe, photoinduced, near-resonant magneto-optical Kerr effect between 1.44 and 1.63 eV. Three components with different temporal and spectral behavior are distinguished in both Kerr rotation and ellipticity, and their origin is discussed in relation with theoretical predictions and simulations. Two contributions are attributed to the splitting of the spin sublevels. The first one, present only as long as pump and probe pulses coincide in time, is a coherent response accounted for in terms of the optical Stark effect, whereas the longer decay of the second one, up to 35 ps, is attributed to electron spin relaxation. The third component is assumed to arise from the difference in population of the photoexcited states and decays within a time smaller than the pulse duration, which is attributed to the energy relaxation of electrons towards the bottom of the conduction band through carrier-carrier and carrier-phonon scattering.

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Initial thermalization of photoexcited carriers in GaAs studied by femtosecond luminescence spectroscopy

Cited by 299 publications

References 18 publications

Nonlinear hole transport through a submicron-size channel

Nonlinear hole transport through a submicron-size channel

Dephasing in InAs/GaAs quantum dots

Room-temperature ultrafast carrier and spin dynamics in GaAs probed by the photoinduced magneto-optical Kerr effect

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