High-performance GaAs nanowire cathode for photon-enhanced thermionic emission solar converters

Liu, Lei; Diao, Yu; Xia, Sihao

doi:10.1007/s10853-018-03231-8

Cited by 54 publications

(24 citation statements)

References 19 publications

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“…8 The vacuum devices based on GaAs nanowires, ie, GaAs nanowire photocathodes, have also been proposed in recent years. [9][10][11] The negative electron affinity (NEA) state of GaAs photocathodes is commonly obtained by depositing Cs and oxidant layers (eg, O 2 or NF 3 ) on the ultra-clean p-type doping GaAs surfaces, resulting in a low vacuum level below the conduction band minimum (CBM). 12 Based on our previous work, Cs-only and Cs/O co-adsorption on (10-10) surfaces of Zn-doped GaAs nanowires can effectively reduce the material work function, predicting an available method to prepare NEA GaAs nanowire photocathodes.…”

Section: Discussionmentioning

confidence: 99%

“…13,14 Experimental observation has proved that wurzite structure GaAs nanowires are more stable than zinc-blende structure when the nanowire diameter is below 15 nm. In addition, the natural cleavage planes (10-10) of wurzite structure have lower surface energy compared with (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) planes. 27 Thus, the clean (10-10) surfaces of wurzite GaAs nanowire are established to simulate the surface activation basement.…”

Section: Computational Detailsmentioning

confidence: 99%

“…Particular interest is directed to GaAs nanowire materials due to their wide applications in lasers, solar cells, and sensors . The vacuum devices based on GaAs nanowires, ie, GaAs nanowire photocathodes, have also been proposed in recent years . The negative electron affinity (NEA) state of GaAs photocathodes is commonly obtained by depositing Cs and oxidant layers (eg, O 2 or NF 3 ) on the ultra‐clean p‐type doping GaAs surfaces, resulting in a low vacuum level below the conduction band minimum (CBM) .…”

Section: Introductionmentioning

confidence: 99%

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Comparative study of negative electron affinity GaAs nanowire photocathodes with Cs/O and with Cs/NF₃from first‐principles

2019

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Summary We perform a detailed comparative study of Cs/O and Cs/NF3 activation mechanism of negative electron affinity (NEA) GaAs nanowire photocathodes through first‐principles calculations based on density functional theory (DFT). The adsorption energy, Mulliken charge distribution, work function, electron affinity, and dipole moment are analyzed. Results show that the stability of Cs/NF3 co‐adsorption nanowire surface is stronger than that of the Cs/O model. The incorporation of O or NF3 on Cs‐covered nanowire surfaces leads to a sharper decline of surface work function. The NEA states can be attained with both O2 and NF3. However, during the Cs/O activation process, it needs to strictly control the Cs/O ratio to achieve the maximum photoemission properties of cathode. Moreover, the work function variation of GaAs nanowire photocathodes activated with Cs, O, and NF3 can be explained by the dipole moment model. This work is expected to provide a theoretical guide for improving Cs/O and Cs/NF3 activation procedure for NEA GaAs nanowire photocathodes.

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Section: Discussionmentioning

confidence: 99%

Section: Computational Detailsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Comparative study of negative electron affinity GaAs nanowire photocathodes with Cs/O and with Cs/NF₃from first‐principles

2019

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“…We suppose that electrical parameters of GaN nanowire are consistent with the bulk GaN material . The effects of temperature on mobility, diffusion coefficient, electron lifetime, and space charge are not considered . In addition, the effects of quantum and size have also been ignored …”

Section: Model and Derivationmentioning

confidence: 99%

“…23,25,26 The effects of temperature on mobility, diffusion coefficient, electron lifetime, and space charge are not considered. 34,35 In addition, the effects of quantum and size have also been ignored. 22,26…”

Section: Model and Derivationmentioning

confidence: 99%

Comparison of quantum and collection efficiency of field‐assisted uniform‐doping and exponential‐doping GaN nanowire cathodes

Liu

2020

Int J Energy Res

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Summary The field‐assisted method is proposed to increase electron capture of the GaN nanowire cathode. We deduce the photoemission or electron collection efficiencies of the field‐assisted uniform‐doping and exponential‐doping cathodes using the diffusion‐drift formula. Results show that the external electric field has a significantly better collection efficiency for uniform‐doping nanowire cathodes than that of exponential‐doping. In cathodes without a build‐in field, quantum efficiency and collection efficiency reached a maximum at incident angles of 65° and 45°, and field intensity of 0.1 and 0.7 V/μm, respectively. The external electric field also contributes to the polarization of GaN nanowires. The field‐assisted GaN NWAs (nanowirearray) cathode could improve the photoemission performance and are expected to be realized in the follow‐up experiment.

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Enhancement of Electron Collection and Light Trapping of Inclined GaN and AlGaN Nanowire Arrays

Liu

Zhangyang

2021

Energy Tech

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The structural design of excellent absorption and electron collection is the main challenge of the nanowire array (NWA) photocathode. Herein, the light trapping and photoemission performance of GaN and graded compositional AlGaN‐inclined NWA are systematically researched. The finite‐difference time domain method (FDTD) is used to calculate the light absorption under different inclined angles and array spacings. The results show that the NWA with an inclined angle of 0.4°–0.6° has greater light‐trapping capacity, which obtains up to 97% light absorption at a wavelength of 267 nm. The inclined graded compositional AlGaN NWA with a built‐in electric field has better photoemission performance. The external electric field further improves the electron collection capacity of the NWA cathode. The inclined AlGaN NWA cathode with the best parameters θ = 0.6°, L = 180 nm, and Eout = 2 V μm−1 obtains a quantum efficiency of 47.57% and collection efficiency of 31.09%. The study of the inclined graded compositional AlGaN NWA cathode assisted by the electric field provides an effective method for further utilization of incident light and emitted electrons.

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High-performance GaAs nanowire cathode for photon-enhanced thermionic emission solar converters

Cited by 54 publications

References 19 publications

Comparative study of negative electron affinity GaAs nanowire photocathodes with Cs/O and with Cs/NF₃from first‐principles

Comparative study of negative electron affinity GaAs nanowire photocathodes with Cs/O and with Cs/NF₃from first‐principles

Comparison of quantum and collection efficiency of field‐assisted uniform‐doping and exponential‐doping GaN nanowire cathodes

Enhancement of Electron Collection and Light Trapping of Inclined GaN and AlGaN Nanowire Arrays

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High-performance GaAs nanowire cathode for photon-enhanced thermionic emission solar converters

Cited by 54 publications

References 19 publications

Comparative study of negative electron affinity GaAs nanowire photocathodes with Cs/O and with Cs/NF3from first‐principles

Comparative study of negative electron affinity GaAs nanowire photocathodes with Cs/O and with Cs/NF3from first‐principles

Comparison of quantum and collection efficiency of field‐assisted uniform‐doping and exponential‐doping GaN nanowire cathodes

Enhancement of Electron Collection and Light Trapping of Inclined GaN and AlGaN Nanowire Arrays

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Comparative study of negative electron affinity GaAs nanowire photocathodes with Cs/O and with Cs/NF₃from first‐principles

Comparative study of negative electron affinity GaAs nanowire photocathodes with Cs/O and with Cs/NF₃from first‐principles