Pre-Emission Study of Photoelectron Dynamics in a GaAs/AlGaAs Photocathode

Jani, Hemang; Chen, Liang; Duan, Lingze

doi:10.1109/jqe.2019.2960774

Cited by 9 publications

(10 citation statements)

References 57 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: 74%

“…The above theoretical model can be experimentally verified by means of femtosecond PPR measurement, which probes the transient variation of the surface reflectivity following the injection of an ultrafast laser pulse. According to the wellknown Drude theory 21,22 , the accumulation of free electrons on the surface of a semiconductor causes a slight change of the surface reflectivity, and the amount of this change is proportional to the area density of the electrons 16 , which is directly correlated to the total electron population N(t) in our 1D model as mentioned earlier. Thus, transient evolutions of N(t) such as those shown in Fig.…”

Section: Theory-experiments Comparisonsmentioning

confidence: 88%

“…Our theory is built upon a two-layer model previously developed for uniform-doped GaAs photocathodes 16 . To incorporate directional carrier drift, we first note that, in a gradient-doped semiconductor photocathode, the p-type doping concentration varies exponentially with depth (such a device is also known as exponential-doped).…”

Section: Theoretical Modelmentioning

confidence: 99%

“…Meanwhile, an important application of III-V photocathodes is the generation of electron bunches using pulsed lasers [12][13][14][15] . Pulsed lasers have also been utilized to investigate the carrier-diffusion dynamics in GaAs photocathodes 12,13,16 . The existing steady-state theories are incapable of describing photoelectron transportation in these cases, and a timedependent, dynamic model has become necessary.…”

Section: Introductionmentioning

confidence: 99%

“…The existing steady-state theories are incapable of describing photoelectron transportation in these cases, and a timedependent, dynamic model has become necessary. Previously, we have developed a diffusion model to explain the behaviors of the photoelectrons in a uniform-doped GaAs photocathode following its excitation by a femtosecond laser pulse 16,17 . In this paper, we generalize the theory to incorporate a built-in electric field and thereby include carrier drift.…”

Section: Introductionmentioning

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: 74%

Section: Theory-experiments Comparisonsmentioning

confidence: 88%

Section: Theoretical Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Photoelectron Transportation Dynamics in GaAs Photocathodes

Zhou,

Jani,

Zhang

et al. 2021

Preprint

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Dynamic photoelectron transport in stepwise-doped GaAs photocathodes

Zhou

Jani

Zhang

et al. 2022

Sci Rep

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We present a theoretical model describing photoelectron transport dynamics in stepwise-doped GaAs photocathodes. Built-in electric field caused by the doping structure is analyzed, and the time-evolution of electron concentration in the active layer induced by a femtosecond laser pulse is solved. The predictions of the model show excellent agreement with the experimental data measured with pump-probe transient reflectometry, demonstrating the capability of the theoretical model in predicting photoelectron behaviors in real devices. Comparisons are also made between this stepwise doping model and the conventional gradient doping model with a continuous doping profile, thereby providing the first quantitative evaluation of the effectiveness and the limitation of the gradient doping model in describing actual stepwise-doped devices.

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Photoelectron transportation dynamics in GaAs photocathodes

Zhou

Jani

Zhang

et al. 2021

Journal of Applied Physics

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We report here a general theory describing photoelectron transportation dynamics in GaAs semiconductor photocathodes. Gradient doping is incorporated into 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 a carrier-induced transient reflectivity change, which is measured for gradient-doped and uniform-doped photocathodes using femtosecond pump–probe reflectometry. An 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.

show abstract

Pre-Emission Study of Photoelectron Dynamics in a GaAs/AlGaAs Photocathode

Cited by 9 publications

References 57 publications

Photoelectron Transportation Dynamics in GaAs Photocathodes

Photoelectron Transportation Dynamics in GaAs Photocathodes

Dynamic photoelectron transport in stepwise-doped GaAs photocathodes

Photoelectron transportation dynamics in GaAs photocathodes

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