Ultrafast relaxation of photoexcited holes in<i>n</i>-doped III-V compounds studied by femtosecond luminescence

Xq, Zhou; Leo, K.; Kurz, H.

doi:10.1103/physrevb.45.3886

Cited by 63 publications

(18 citation statements)

References 20 publications

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“…This is in contrast with the case of n-doped samples where with measurements being performed for doping densities much larger (ϳ10 times͒ than the photoexcited plasma density, the thermal electrons introduced by doping can be considered as a thermal bath for holes. 13,14 The weak dependence of the measured hole relaxation rate on carrier density and its monoexponential behavior suggest that in intrinsic systems, electron-hole scattering is not the main hole heating process and that hole thermalization is essentially due to hole-optical phonon scattering with a dominant contribution from polar interactions. LO phonon absorption by cold holes involves large momentum exchanges ͑for instance, holes at the top of the valence band can only exchange a momentum of ͱ2m HH ប LO /ប) and, in contrast to the electron-LO phonon interaction and to hotcarrier cooling processes, it is thus only weakly reduced by screening in the investigated carrier density range.…”

Section: Resultsmentioning

confidence: 99%

“…12 Specific time-resolved experiments have thus to be designed to selectively access hole relaxation dynamics. [13][14][15][16][17][18][19] Consequently, although electron interaction processes are now relatively well characterized, little is known on hole thermalization dynamics, especially in intrinsic direct-gap semiconductors, except at very high carrier density in the gain regime. 20,21 This problem has recently been addressed in n-doped bulk GaAs and InP and GaAs/Al x Ga 1Ϫx As quantum wells using time-resolved luminescence.…”

Section: Introductionmentioning

confidence: 99%

“…20,21 This problem has recently been addressed in n-doped bulk GaAs and InP and GaAs/Al x Ga 1Ϫx As quantum wells using time-resolved luminescence. 13,14 In these experiments, the high-density thermal electron population introduced by doping acts as a reservoir for the recombination of lowdensity photoexcited hot holes, permitting the determination of their cooling dynamics, but also as a thermal bath dominating hole cooling at low temperatures. 13,14 To suppress this effect, thermalization of a one-component plasma has been studied in p-doped Ge using a femtosecond intervalence band absorption saturation technique.…”

Section: Introductionmentioning

confidence: 99%

“…13,14 In these experiments, the high-density thermal electron population introduced by doping acts as a reservoir for the recombination of lowdensity photoexcited hot holes, permitting the determination of their cooling dynamics, but also as a thermal bath dominating hole cooling at low temperatures. 13,14 To suppress this effect, thermalization of a one-component plasma has been studied in p-doped Ge using a femtosecond intervalence band absorption saturation technique. 16,17 These measurements, performed at low temperature, show contributions of both scattering of nonequilibrium holes by the background thermal holes and of hole-phonon interactions.…”

Section: Introductionmentioning

confidence: 99%

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Nonequilibrium hole relaxation dynamics in an intrinsic semiconductor

1996

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The thermalization dynamics of photoexcited nonequilibrium holes is selectively investigated in intrinsic bulk GaAs using a high sensitivity two-wavelength pump-probe technique. The carriers are photoexcited close to the bottom of their respective bands and hole heating is followed by monitoring the absorption saturation due to filling of higher-energy states. The characteristic thermalization time is measured to increase only slightly from ϳ120 to ϳ170 fs as carrier density decreases from 7ϫ10 17 to 2ϫ10 16 cm Ϫ3 , indicating that hole heating is dominated by hole-optical-phonon scattering. These results are in good agreement with a simulation of the carrier relaxation based on numerical resolution of the carrier Boltzmann equations including interaction of holes with LO and TO phonons. ͓S0163-1829͑96͒10327-1͔

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nonequilibrium hole relaxation dynamics in an intrinsic semiconductor

1996

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“…3 Only in a few specific experiments could information on the hole relaxation dynamics be obtained in special sample structures. [4][5][6][7][8] In these studies, holes were excited with a certain excess energy and subsequent cooling processes were observed. In contrast, optical excitation of excitons close to the band edge will create initially cold holes.…”

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confidence: 99%

Time-resolved study of intervalence band thermalization in a GaAs quantum well

Kim

Hunsche

Dekorsy

et al. 1996

Applied Physics Letters

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The thermalization of optically excited cold holes in a GaAs quantum well is investigated by femtosecond two-color pump-probe measurements. Clear evidence is found for scattering from heavy-holes into the lowest light-hole band due to LO-phonon absorption. We obtain firm data on scattering times which depend strongly on lattice temperature. They vary from 230 fs at room temperature to 900 fs at Tϭ105 K. The experimental data are well reproduced by numerical calculations. © 1996 American Institute of Physics. ͓S0003-6951͑96͒03021-5͔Firm experimental data on ultrafast carrier dynamics in semiconductors and semiconductor heterostructures are of prime importance for the development of novel ultrafast opto-electronic devices. The development of ultrashort-pulse lasers has stimulated a large number of time-resolved studies addressing the picosecond and subpicosecond dynamics of nonequilibrium carriers in GaAs and other III-V semiconductors. 1,2 Since the density of states in the conduction band is generally much lower than that of the valence band, in most studies the experimental signals are dominated by the dynamics of optically excited electrons. 3 Only in a few specific experiments could information on the hole relaxation dynamics be obtained in special sample structures. [4][5][6][7][8] In these studies, holes were excited with a certain excess energy and subsequent cooling processes were observed. In contrast, optical excitation of excitons close to the band edge will create initially cold holes. In this case, the hole dynamics at elevated lattice temperatures is expected to be dominated by the absorption of longitudinal optical ͑LO͒ phonons that leads to a heating of the initial hole distribution. 3,7 In this letter, we investigate the intervalence band thermalization of optically excited holes. Femtosecond timeresolved measurements of the bleaching of the heavy-hole ͑HH͒ and light-hole ͑LH͒ exciton transition in a GaAs multi quantum well ͑MQW͒ sample are performed. The nonlinear absorption of the excitonic transitions is determined by two contributions, namely the reduction of the oscillator strength and the broadening of the exciton line. 9 It has been shown previously that the reduction of the oscillator strength strongly depends on the subband occupation number, while the intrasubband carrier distribution does not play a significant role. 9,10 In the same work it was found that broadening is not affected by changes of the subband occupation. Furthermore, measurements of absorption changes at the lowenergy edge of the E1H1 transition-which are dominated by broadening-under various excitation conditions only show an ''instantaneous'' signal without any further dynamics on a picosecond time scale, indicating that this signal contribution is not sensitive to the exact intrasubband carrier distribution, either. 11 These facts make it possible to measure changes of the hole subband occupation by choosing sample and excitation parameters that prevent any electron intersubband dynamics.Our experiments are performed...

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