Influence of the p-type doping concentration on reflection-mode GaN photocathode

Wang, Xiaohui; Chang, Benkang; Ren, Ling; Gao, Pin

doi:10.1063/1.3556656

Cited by 57 publications

(27 citation statements)

References 20 publications

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“…This equation has been very fruitful in practice and continues to be used to model NEA photocathodes. 14,15 However, this relation makes two simplifications: it assumes that the cathode is semi-infinite in extent, and that every electron reaching the surface either escapes or recombines there. Further models have relaxed these assumptions independently, 9,[16][17][18] yet for most applications it has not been necessary to relax both simplifications simultaneously and examine the interplay between thickness and recombination.…”

Section: Introductionmentioning

confidence: 99%

A model for emission yield from planar photocathodes based on photon-enhanced thermionic emission or negative-electron-affinity photoemission

Sahasrabuddhe

Schwede

Bargatin

et al. 2012

Journal of Applied Physics

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A general model is presented for electron emission yield from planar photocathodes that accounts for arbitrary cathode thickness and finite recombination velocities at both front and back surfaces. This treatment is applicable to negative electron affinity emitters as well as positive electron affinity cathodes, which have been predicted to be useful for energy conversion. The emission model is based on a simple one-dimensional steady-state diffusion treatment. The resulting relation for electron yield is used to model emission from thinfilm cathodes with material parameters similar to GaAs. Cathode thickness and recombination at the emissive surface are found to strongly affect emission yield from cathodes, yet the magnitude of the effect greatly depends upon the emission mechanism. A predictable optimal film thickness is found from a balance between optical absorption, surface recombination, and emission rate. Disciplines Mechanical EngineeringComments Sahasrabuddhe, K., Schwede, J., Bargatin, I., Jean, J., Howe, R., Shen, Z., & Melosh, N. (2012). A model for emission yield from planar photocathodes based on photon-enhanced thermionic emission or negativeelectron-affinity photoemission. Journal of Applied Physics, 112(9) A general model is presented for electron emission yield from planar photocathodes that accounts for arbitrary cathode thickness and finite recombination velocities at both front and back surfaces. This treatment is applicable to negative electron affinity emitters as well as positive electron affinity cathodes, which have been predicted to be useful for energy conversion. The emission model is based on a simple one-dimensional steady-state diffusion treatment. The resulting relation for electron yield is used to model emission from thin-film cathodes with material parameters similar to GaAs. Cathode thickness and recombination at the emissive surface are found to strongly affect emission yield from cathodes, yet the magnitude of the effect greatly depends upon the emission mechanism. A predictable optimal film thickness is found from a balance between optical absorption, surface recombination, and emission rate.

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Section: Introductionmentioning

confidence: 99%

A model for emission yield from planar photocathodes based on photon-enhanced thermionic emission or negative-electron-affinity photoemission

Sahasrabuddhe

Schwede

Bargatin

et al. 2012

Journal of Applied Physics

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“…After the samples A, B and D were sent into the ultra-high vacuum chamber, the samples were thermally cleaned at 710 • C as the traditional thermal cleaning temperature of the GaN and AlGaN photocathode. Next they were activated by Cs adsorption, and the photocurrent was measured on-line by the multi-information system [6,[17][18][19]. Until the photocurrent was not increased anymore, the quantum efficiency of three samples with photon energy from 4.2 to 5.16 eV was measured.…”

Section: Cleaning Process Of Algan Photocathodesmentioning

confidence: 99%

“…The KOH was the boiling KOH solution, and its concentration was 1 mol/L. The sample A was etched by the sulfuric acid mixed solution for about 10 min, which is the traditional chemical etching method of the GaN and AlGaN photocathode [6,[17][18][19]. The sample B was etched by sulfuric acid mixed solution for about 10 min and KOH solution for about 50 s, respectively.…”

Section: Cleaning Process Of Algan Photocathodesmentioning

confidence: 99%

The effect of surface cleaning on quantum efficiency in AlGaN photocathode

Hao

Zhang

Jin

et al. 2015

Applied Surface Science

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“…Cs, O coadsorption is the most popular method for activation of I-V semiconductor photocathodes to obtain negative electron affinity (NEA), such as GaAs, AlGaAs, GaN, and AlGaN photocathodes [1][2][3][4]. Many experimental researches have been done to study Cs/O proportion and adsorption order to obtain highest photocurrent.…”

Section: Introductionmentioning

confidence: 99%

Cesium, oxygen coadsorption on AlGaN(0001) surface: experimental research and ab initio calculations

Yang

Chang

Wang

2015

J Mater Sci: Mater Electron

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Cs, O activation experiment of Al 0.24 Ga 0.76 N photocathodes was carried out and the photocurrent variation was recorded. Then first principle calculations were performed to study Cs, O coadsorption on Al 0.25 Ga 0.75-N(0001) surface. Three surface models were built, one model represents pure surface, and the other two are defective surface models with Ga or N vacancy on the topmost layer. Cs only adsorption systems were built based on clean surface, and Cs, O coadsorption systems were built based on the three surfaces. Work function, average dipole charge, average dipole length, and dipole moments were calculated. Results show there exist double dipoles in the Cs, O coadsorbed Al 0.25 Ga 0.75 N(0001) surfaces. One is Cs-induced dipole [Cs-Al 0.25 Ga 0.75 N], which was caused by electrons transferring from Cs adatoms to Al 0.24 Ga 0.75 N substrate. This dipole is perpendicular to surface, and it is helpful for electrons escaping to vacuum. The other dipole [Cs-O] is composed of Cs and O adatoms, which is induced by electrons transferring from the Cs adatoms to O adatoms. Cs, O coadsorption results in lower work function on defective Al 0.24 Ga 0.75 N(0001) surfaces than the pure one. The reason is that the direction of [Cs-O] dipole on the defective surface is oriented to the substrate. Nevertheless, the direction difference between [Cs-O] dipole and surface without defect is too small to lower work function significantly. This work gives theoretical explanation for photocurrent variation and dipole moments formation of Cs, O coadsorbed AlGaN photocathodes.

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Influence of the p-type doping concentration on reflection-mode GaN photocathode

Cited by 57 publications

References 20 publications

A model for emission yield from planar photocathodes based on photon-enhanced thermionic emission or negative-electron-affinity photoemission

A model for emission yield from planar photocathodes based on photon-enhanced thermionic emission or negative-electron-affinity photoemission

The effect of surface cleaning on quantum efficiency in AlGaN photocathode

Cesium, oxygen coadsorption on AlGaN(0001) surface: experimental research and ab initio calculations

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