Influence of Al fraction on photoemission performance of AlGaN photocathode

Hao, Gazi; Chang, Benkang; Shi, Feng; Zhang, Junju; Zhang, Yijun; Chen, Xinlong; Jin, Muchun

doi:10.1364/ao.53.003637

Cited by 24 publications

(5 citation statements)

References 18 publications

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“…The quantum efficiency curves are shown in Fig. 6, where the peak quantum efficiency of T3 sample is 23.9% and that of T2 sample is 18.9%, which is consistent with the reported peak quantum efficiency of GaAlN photocathode with the same structure and Al component [12,13] . As can be seen from Figure 6, T3 has a significantly higher quantum efficiency than the T2 sample over the entire response band range, and both samples correspond to the designed cut-off response wavelength at 1% quantum efficiency.…”

Section: Experimental Results and Analysissupporting

confidence: 87%

Measurement and analysis of surface photovoltage of GaAlN material with multi-layer structrues

Liu,

Zhang,

Qian

2023

Third International Computing Imaging Conference (CITA 2023)

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Three kinds of transmission type GaAlN photocathode materials with GaAlN activation layer/GaAlN absorber layer/AlN buffer layer/Al2O3 substrate layer multi-layer structures with different Al compositions were designed and grown. The thickness of the GaAlN activation layer, the GaAlN absorber layer and the AlN buffers layer of the three samples were 40 nm, 20 nm and 100 nm respectively. The Al fraction of the GaAlN activation layer of the three samples were 0.48, 0.37 and 0.25 respectively, and the Al fraction of GaAlN absorber layer were 0.8, 0.68 and 0.3 respectively. An ultraviolet waveband surface photovoltage testing device was developed for the measurement of the characteristics of surface photovoltage of the three GaAlN photocathode materials. The surface photovoltage amplitude curves of the three samples were basically the same under the two cases of frontal and reverse incidence, and the surface photovoltage signals obtained by the two different light incidence methods were differentiated, and the extreme points of the differentiation curves were obtained near the positions of 4.47 eV, 4.21 eV and 3.92 eV respectively, which correspond to the forbidden band width of the GaAlN material in the activation layer of the three samples. Comparing the surface photovoltage curves before activation with the spectral response curves after activation of two samples, it is found that the surface photovoltage curves before activation and the spectral response curves after activation are highly consistent in characteristics of spectral response and cut-off, which proves the effectiveness of surface photovoltage in the evaluation of characteristics of the spectral response of the GaAlN photocathode materials with multi-layer structures.

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Section: Experimental Results and Analysissupporting

confidence: 87%

Measurement and analysis of surface photovoltage of GaAlN material with multi-layer structrues

Liu,

Zhang,

Qian

2023

Third International Computing Imaging Conference (CITA 2023)

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“…Both the AlGaAs and AlGaN samples were etched by H 2 SO 4 :H 2 O 2 :H 2 O solution with different ratios of 4:1:100 for two minutes and 2:2:1 for ten minutes due to the different etching ability. After being rinsed by deionized water and dried in air, the two photocathode samples were transferred into the ultra-high vacuum system which the base pressure was less than 3.3×10 -8 Pa and heated in vacuum at 650℃ (AlGaAs sample) and 710°C (AlGaN sample) for twenty minutes [28][29][30]. When the samples cooled to room temperature, an activation experiment was performed on high quality p-type Zn-doped AlGaAs substrate and p-type Mg-doped AlGaN substrate grown by metal organic chemical vapor deposition (MOCVD).…”

Section: ) Photocurrentmentioning

confidence: 99%

Comparative Research on Cs Activation Mechanism for Al0.5Ga0.5As (001) and Al0.25Ga0.75N (0001) Surface

Shen

Chen

et al. 2015

IEEE Sensors J.

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To investigate and distinguish the difference of Cs activation mechanism on Al 0.5 Ga 0.5 As (001) and Al 0.25 Ga 0.75 N (0001) surface, plane wave with ultrasoft pseudopotential method based on first-principle density functional theory (DFT) is used. Surface adsorption energy, work function and surface dipole moments with different Cs coverage are calculated and compared. Eight possible Cs adsorption sites are chosen for the Al 0.5 Ga 0.5 As (001) surface while seven high-symmetry sites are considered in the calculation model of Al 0.25 Ga 0.75 N (0001) surface. Results show that when only one Cs atom adsorbed on two surfaces, the adsorption energies are all negative and the adsorption sites are all stable sites. The lowest work function and the most stable adsorption sites with different Cs coverage are obtained and discussed. When different amounts of Cs atoms adsorbed on two surfaces, the work function values of Al 0.25 Ga 0.75 N (0001) surface are all smaller than that of Al 0.5 Ga 0.5 As (001) surface. The work function of Al 0.5 Ga 0.5 As (001) surface decreases with the increase of Cs coverage when the Cs coverage changes from 0 monolayer (ML) to 0.75 ML, while Al 0.25 Ga 0.75 N (0001) surface achieves the smallest work function when the Cs coverage is 0.5 ML. Finally, photocurrent curves during Cs activation are recorded. The photocurrent of AlGaAs sample reaches at a peak at the time of 29 min when the Cs coverage rise at 0.75 ML, while the photocurrent of AlGaN sample achieves a peak at the time of 30 min when the Cs coverage rise at 0.5 ML, which is in well consistent with our calculation results.

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“…As a result, the electrons are readily emitted from the surface. Co-adsorption of Cs and oxygen on the cathode surface is an effective method for activating semiconductor photocathodes and achieving NEA in materials such as GaAs, 8,9) AlGaAs, 10) GaN 11) and AlGaN [12][13][14][15] photocathodes. However, these reports are limited to the photocathode of p-type semiconductors, not the co-deposition of Cs and oxygen on n-type AlGaN for the thermal cathode.…”

Section: Introductionmentioning

confidence: 99%

Surface activation of n-type AlGaN with cesium and oxygen to enhance thermionic emission

Namura,

Kimura,

Miyazaki

et al. 2024

Jpn. J. Appl. Phys.

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The paper describes the characteristics of thermionic emission of AlGaN surface through surface control employing cesium (Cs) and oxygen. The thermionic emission current of AlGaN surfaces with Cs and oxygen was measured, and the surface state of AlGaN was analyzed by employing a new material-independent thermionic emission model (MRM) based on the Richardson-Dushman equation successfully reproduced the thermionic emission behavior of Cs-deposited and Cs/O2 co-deposited AlGaN, considering the dynamic change of the surface layer caused by thermal desorption of Cs. These results indicate that AlGaN co-deposited with Cs/O2 could be applied as a thermionic energy converter operating in a lower to medium temperature range (200-800 °C), as compared to conventional devices.

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Influence of Al fraction on photoemission performance of AlGaN photocathode

Cited by 24 publications

References 18 publications

Measurement and analysis of surface photovoltage of GaAlN material with multi-layer structrues

Measurement and analysis of surface photovoltage of GaAlN material with multi-layer structrues

Comparative Research on Cs Activation Mechanism for Al<sub>0.5</sub>Ga<sub>0.5</sub>As (001) and Al<sub>0.25</sub>Ga<sub>0.75</sub>N (0001) Surface

Surface activation of n-type AlGaN with cesium and oxygen to enhance thermionic emission

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