Time-Frequency Spectroscopy of 
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mrow><mml:mi>Ga</mml:mi><mml:mi>As</mml:mi></mml:mrow></mml:math>
 Transient Dispersion Using Few-Cycle Pump-Probe Reflectometry

Jani, Hemang; Duan, Lingze

doi:10.1103/physrevapplied.13.054010

Cited by 10 publications

(4 citation statements)

References 45 publications

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“…As such, the model is capable of describing devices with arbitrary doping gradients. We further verify the model by comparing it with experimental results from femtosecond pump-probe reflectometry (PPR) measurements 16,18 . Good experiment-theory agreements are realized, demonstrating the effectiveness of the theory in modeling real devices.…”

Section: Introductionmentioning

confidence: 73%

“…Experimental measurement of ∆R(t) has been performed using a home-built PPR system, which is based on a 6.5fs Ti:sapphire laser operating at a center wavelength of 800 nm, with an average power of 500 mW and a repetition rate of 83 MHz. More details about the system can be found elsewhere 16,18 . Several samples of GaAs photocathodes have been tested, including two gradient-doped devices, one fabricated with metal organic chemical vapor deposition (MOCVD) and the other fabricated with molecular-beam epitaxy (MBE).…”

Section: Theory-experiments Comparisonsmentioning

confidence: 99%

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Photoelectron Transportation Dynamics in GaAs Photocathodes

Zhou,

Jani,

Zhang

et al. 2021

Preprint

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We report here a general theory describing photoelectron transportation dynamics in GaAs semiconductor photocathodes. Gradient doping is incorporated in the model through the inclusion of directional carrier drift. The time-evolution of electron concentration in the active layer upon the injection of an excitation pulse is solved both numerically and analytically. The predictions of the model are compared with experiments via carrier-induced transient reflectivity change, which is measured for gradient-doped and uniform-doped photocathodes using femtosecond pump-probe reflectometry. Excellent agreement is found between the experiments and the theory, leading to the characterization of key device parameters such as diffusion constant and electron decay rates. Comparisons are also made between uniform doping and gradient doping for their characteristics in photoelectron transportation. Doping gradient is found to be able to accelerate electron accumulation on the device surface. These results offer new insights into the dynamics of III-V photocathodes and potentially open a new avenue toward experimental characterization of device parameters.

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Section: Introductionmentioning

confidence: 73%

Section: Theory-experiments Comparisonsmentioning

confidence: 99%

Photoelectron Transportation Dynamics in GaAs Photocathodes

Zhou,

Jani,

Zhang

et al. 2021

Preprint

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“…In the last decades, setups for ultrafast optical measurements (see for example Refs. 8,14,15 ) have been becoming increasingly available in many laboratories worldwide. Nonetheless, systematic measurements under similar pump-probe conditions have been rarely reported, even for simple materials such as silicon, germanium or gallium arsenide, subjects of the present study.…”

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confidence: 99%

“…More recently, data and interpretation were extended for silicon to a wider optical range 4 . Several transient reflectivity works 5,15,17,18 regarded also GaAs and specific models taking into account the filling of valence band, band modification and the free carrier absorption were developed 19,20 . To the best of our knowledge, there are no previous pump-probe reflectivity works on germanium, but time-resolved dielectric function data in the visible range 21 and models for the interpretation have been proposed 22,23 .…”

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confidence: 99%

Broadband optical ultrafast reflectivity of Si, Ge and GaAs

Cicco

Polzoni

Gunnella

et al. 2020

Sci Rep

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Ultrafast optical reflectivity measurements of silicon, germanium, and gallium arsenide have been carried out using an advanced set-up providing intense subpicosecond pulses (35 fs FWHM, $$\lambda $$ λ = 400 nm) as a pump and broadband 340–780 nm ultrafast pulses as a white supercontinuum probe. Measurements have been performed for selected pump fluence conditions below the damage thresholds, that were carefully characterized. The obtained fluence damage thresholds are 30, 20.8, 9.6 mJ/$$\hbox {cm}^2$$ cm 2 for Si, Ge and GaAs respectively. Ultrafast reflectivity patterns show clear differences in the Si, Ge, and GaAs trends both for the wavelength and time dependences. Important changes were observed near the wavelength regions corresponding to the $$E_1$$ E 1 , $$E_1+\Delta $$ E 1 + Δ singularities in the joint density of states, so related to the peculiar band structure of the three systems. For Ge, ultrafast reflectivity spectra were also collected at low temperature (down to 80 K) showing a shift of the characteristic doublet peak around 2.23 eV and a reduction of the recovery times.

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