Hot-Electron Relaxation in GaAs Quantum Wells

Yanɡ, Chao; Carlson-Swindle, Jean M.; Lyon, S. A.; Worlock, J. M.

doi:10.1103/physrevlett.55.2359

Cited by 140 publications

(39 citation statements)

References 15 publications

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“…Although the total optical excess energies are more than a LO phonon energy, the emission of LO phonons plays a minor role as a scattering mechanism in the valence band, since most of the excess energy is transferred to the conduction band. At 75 meV excess energy the excess energy of electrons is nearly twice the LO phonon energy resulting in a relaxation of the electrons within some 100 fs [14]. The observations in the EOTC are confirmed in the TC, while the FWM signals exhibit only a correlationlike peak at all excess energies.…”

Section: -9007͞96͞77supporting

confidence: 66%

“…This is the result of the inhomogeneous broadening introduced by the band dispersion and an increased k space for momentum scattering. Additionally, energy relaxation by LO phonon emission is expected to take place in the conduction band within 170 fs [14]. The decrease of the dephasing time by less than a factor of 2 in the transmission experiments indicates only a small increase of the intraband dephasing processes of continuum states in the valence band under OR excitation.…”

Section: -9007͞96͞77mentioning

confidence: 99%

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Quantum Coherence of Continuum States in the Valence Band of GaAs Quantum Wells

et al. 1996

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Quantum beats of heavy and light holes in GaAs quantum wells are investigated in femtosecond time-resolved four-wave mixing and transmission experiments as a function of optical excitation energy. Under nonexcitonic excitation conditions, the four-wave mixing signal disappears due to the immediate loss of the interband coherence of continuum states. In the transmission experiment, the quantum beats are observed up to excess energies of 75 meV above the exciton resonances.The experimental data clearly demonstrate the coherence of continuum states in the valence band. Changes of the beat frequency with the excitation energy are due to the dispersion of the valence bands.[ S0031-9007(96) Time-resolved investigations of quantum beats in semiconductor quantum wells have received considerable attention in the last few years, since they provide insight into the scattering and coupling mechanisms between light, excitons, free carriers, and phonons in these systems. Most of this work deals with quantum coherence of excitonic states, which may have dephasing rates up to some picoseconds at low lattice temperatures in GaAs based heterostructures. The most commonly used tool for the time-resolved detection of optically excited coherence in semiconductors is four-wave mixing (FWM) spectroscopy [1]. In self-diffracted degenerate FWM, the third order nonlinear interband polarization is detected, which gives a selective sensitivity for the excitonic coherence based on two facts: (i) The signal is proportional to the eighth order of the transition matrix elements [2], which is significantly enhanced at the exciton energy, and (ii) continuum states lose their interband coherence on a time scale of 100 fs resulting in the dominance of the long-living excitonic contribution [3]. The immediate loss of the interband coherence of continuum states arises from the k-space band dispersion, which is equivalent to an "inhomogeneous" broadening of interband transitions with the energetic width of the exciting laser spectrum. Furthermore, the excitation of continuum states with excess energy above the band minimum provides additional scattering channels for momentum and energy relaxation so that a decreased interband dephasing time is expected. Several different techniques have been applied for the time-resolved investigation of coherent electronic states in semiconductors, e.g., THz emission spectroscopy [4][5][6], time-resolved transmission spectroscopy [2,7], and time-resolved resonant luminescence up-conversion [8]. All these techniques provide distinctly different information on coherent states than FWM. In THz emission spectroscopy, the detected THz radiation arises from the real space oscillation of coherent wave packets and is thus not necessarily restricted to excitonic transitions. Therefore, under appropriate excitation conditions, the detected signal may give information on the intraband coherence of the excited states. These observations have been made for the case of nonexcitonic excitation of Bloch oscillations in superlattice...

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Section: -9007͞96͞77supporting

confidence: 66%

Section: -9007͞96͞77mentioning

confidence: 99%

Quantum Coherence of Continuum States in the Valence Band of GaAs Quantum Wells

et al. 1996

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“…At low lattice temperatures and low excitation levels, the relation between input power ͑or total energy loss͒ and electron temperature was predicted 33 by P T ϳ(T e n ϪT n ) and in most cases 14 nϳ3. At high lattice temperature and/or high excitation levels, the relation becomes 34 P T ϳ(ប LO /)exp(Ϫប LO /k B T e ) with the effective hotelectron relaxation time. The practical evaluation of electron temperature as a function of input power complicates the numerical calculation considerably, 29 and I do not attempt it in the present paper.…”

Section: Resultsmentioning

confidence: 99%

Emission of acoustic and optical phonons by hot electrons in a two-dimensional electron system in parallel magnetic fields

1996

Phys. Rev. B

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In this paper, we present a detailed theoretical study on acoustic-and optical-phonon emission by hot electrons in Al x Ga 1Ϫx As parabolic quantum wells in parallel magnetic fields. We consider the situation where the phonon generation is detected by phonon emission experiments. The dependence of phonon emission on the magnetic field, excitation power, and phonon emission angle has been studied through calculating the electron energy loss rate in this configuration. The main results obtained from the present theoretical study are the following. ͑i͒ In low-, intermediate-, and high-energy excitations, phonon generation is mainly through electron-phonon interaction via piezoelectric, deformation-potential, and polar-optical coupling, respectively. ͑ii͒ The strongest acoustic-phonon emission can be observed around a magnetic field at which an electronic subband becomes depopulated, and the strongest LO-phonon emission occurs around a magnetic field where the energy spacing between two subbands equals the LO-phonon energy ͑electrophonon resonance effect͒. ͑iii͒ Phonon generation in the presence of parallel magnetic fields has a different angular distribution from that at zero and perpendicular magnetic fields.͓S0163-1829͑96͒016619-0͔

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“…At low enough temperatures k B T ≪hw LO , where ω LO is the frequency of the dispersionless LO phonon, the inclusion of the phonon propagator renormalization may enhance the energy relaxation rate by orders of magnitude compared with loss through bare LO-phonon (which is exponentially small for k B T ≪hω LO ). Deviation from the naive bare-phonon result, which gives an exponentially decaying energy relaxation rate as electron temperature is lowered, is a ubiquitous phenomenon in hot-electron energy loss experiments [5][6][7][8][9], and has usually been uncritically ascribed to acoustic-phonon contribution, in spite of the fact that merely including the acoustic-phonon emission could not account for the total observed power loss. This puzzle is resolved by including the enhancement from the renormalization of the LO-phonon propagator.…”

mentioning

confidence: 99%

“…The study of this subject also constitutes a direct probe of a fundamental interaction in condensed matter physics, namely, the electron-phonon interaction. There has been considerable recent theoretical and experimental interest in the hot-electron energy relaxation problem in polar semiconductors, particularly in three-dimensional (3D) and two-dimensional (2D) GaAs structures [1][2][3][4][5][6][7][8][9]. More recently, one-dimensional (1D) hot-electron relaxation in quantum wire structures has been considered theoretically [10][11][12], motivated by the fact that there has been successful growth of one-dimensional GaAs quantum-well wires with only the lowest subband occupied [13].…”

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confidence: 99%

Energy relaxation of an excited electron gas in quantum wires: Many-body electron-LO-phonon coupling

Zheng

Sarma

1996

Phys. Rev. B

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We theoretically study energy relaxation via LO-phonon emission in an excited one-dimensional electron gas confined in a GaAs quantum wire structure. We find that the inclusion of phonon renormalization effects in the theory extends the LO-phonon dominated loss regime down to substantially lower temperatures. We show that a simple plasmon-pole approximation works well for this problem, and discuss implications of our results for low temperature electron heating experiments in quantum wires.

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Hot-Electron Relaxation in GaAs Quantum Wells

Cited by 140 publications

References 15 publications

Quantum Coherence of Continuum States in the Valence Band of GaAs Quantum Wells

Quantum Coherence of Continuum States in the Valence Band of GaAs Quantum Wells

Emission of acoustic and optical phonons by hot electrons in a two-dimensional electron system in parallel magnetic fields

Energy relaxation of an excited electron gas in quantum wires: Many-body electron-LO-phonon coupling

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