Improved activation technique for preparing high-efficiency GaAs photocathodes

Zhang, Yijun; Qian, Yunsheng; Feng, Cheng; Shi, Feng; Cheng, Hongchang; Zou, Ji‐Jun; Zhang, Jingzhi; Zhang, Xiang

doi:10.1364/ome.7.003456

Cited by 26 publications

(11 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…After thermal purification, the sample was activated by cesium (Cs) and oxygen (O) to lower the surface work function and form NEA surface, thereby improving the escape probability of photoelectrons. The Cs and O activation technology adopted the Cs source continuous and O source intermittent activation method [11] . The background vacuum degree of the activation chamber was better than 3×10 -8 Pa. During activation, the surface of the cathode sample was illuminated with white light from a halogen lamp, the photocurrent and the quantum efficiency curve after the activation were tested in-situ by the multiinformation on-line measurement and control system.…”

Section: Methodsmentioning

confidence: 99%

Application of scanning focused X-ray imaging positioning technique in preparation of GaAs photocathodes

Zhang

Fang

Qian

et al. 2020

Photosensitive Materials and Their Applications

Self Cite

View full text Add to dashboard Cite

Negative-electron-affinity GaAs-based photocathodes have already found widespread application in modern night vision detectors and vacuum electron sources. Considering the importance of surface micro-area analysis for cathode preparation, a new ultrahigh vacuum interconnection system for photocathode preparation and characterization was developed, wherein the scanning focused X-ray imaging positioning technique combined with the X-ray induced secondary electron image was applied to characterize the surface components in the specified micro region of semiconductor photocathodes. With the aid of the advanced characterization technique, the surface components of micro regions of interest for GaAs cathode samples after cleaning and Cs-O activation were analyzed. The experimental results show that the GaAs cathode samples would be subjected to secondary contamination from the metal sheet of sample holder, accompanied by a small amount of sodium and cesium. The subsequent heat treatment and Cs-O activation can hardly remove the sodium contamination, which can affect the arsenic desorption during heat treatment, hinder the Cs-O adsorption in the activation process, and finally reduce the photoemission performance of the activated cathode. Through the application of the X-ray induced secondary electron image, the optimal cleaning method for GaAs cathode was investigated. This surface characterization technique is of practical value to improving analysis accuracy and optimizing the cathode preparation process.

show abstract

Section: Methodsmentioning

confidence: 99%

Application of scanning focused X-ray imaging positioning technique in preparation of GaAs photocathodes

Zhang

Fang

Qian

et al. 2020

Photosensitive Materials and Their Applications

Self Cite

View full text Add to dashboard Cite

show abstract

“…After the sample cooled to room temperature, the Cs▬O activation to form the NEA state at the cathode surface was performed in the UHV chamber with a base pressure of 10 À9 Pa. The Cs and O sources used in the activation are solid dispensers easily controlled by direct current, and the flux is proportional to the operating current [35]. During the activation, the Cs source was on all the time, and the O source was switched on and off [35].…”

Section: Activation Of Photocathode Surfacementioning

confidence: 99%

“…The Cs and O sources used in the activation are solid dispensers easily controlled by direct current, and the flux is proportional to the operating current [35]. During the activation, the Cs source was on all the time, and the O source was switched on and off [35]. The operating current of Cs and O dispensers was regulated by program control current supply, and the photocurrent induced by a white light source was monitored in real time by the computer-controlled test system [35].…”

Section: Activation Of Photocathode Surfacementioning

confidence: 99%

“…During the activation, the Cs source was on all the time, and the O source was switched on and off [35]. The operating current of Cs and O dispensers was regulated by program control current supply, and the photocurrent induced by a white light source was monitored in real time by the computer-controlled test system [35]. The initial Cs supply caused the gradual increase of the photocurrent.…”

Section: Activation Of Photocathode Surfacementioning

confidence: 99%

See 1 more Smart Citation

Energy Bandgap Engineering of Transmission-Mode AlGaAs/GaAs Photocathode

Zhang¹,

Jiao²

2018

Photodetectors [Working Title]

Self Cite

View full text Add to dashboard Cite

Aiming to enhance the photoemission capability in the waveband region of interest, a graded bandgap structure was applied to the conventional transmission-mode AlGaAs/ GaAs photocathodes based on energy bandgap engineering, wherein the composition in Al x Ga 1Àx As window layer and the doping concentration in GaAs active layer were gradual. According to Spicer's three-step model, a photoemission theoretical model applicable to the novel transmission-mode Al x Ga 1Àx As/GaAs photocathodes was deduced so as to guide the cathode structural design. Then the cathode material was grown by the metalorganic chemical vapor deposition technique, and the epitaxial cathode material quality was evaluated by the means of scanning electron microscope, electrochemical capacitance-voltage, X-ray diffraction and spectrophotometry. Through a series of specific processes, the cathode material was made into the multilayered module, possessing a glass/Si 3 N 4 /Al x Ga 1Àx As/GaAs structure. After the surface treatment including heat cleaning and Cs▬O activation for the cathode module, the image intensifier tube comprising the activated cathode module, microchannel plate, and phosphor screen was fabricated by indium sealing. The spectral response test results confirm the validity of the novel structure for the enhancement of blue-green photoresponse.

show abstract

“…But despite this exciting result and others [27][28], it remains difficult to fabricate p-n junctions and electrodes of typical diodetype devices such as solar cells using nano-scaled resonators. In contrast, for a NEA photocathode, where the required bias can be applied externally and only p-doped GaAs is needed [9,15], the fabrication process is much simpler.…”

mentioning

confidence: 99%

Optical-Resonance-Enhanced Photoemission from Nanostructured GaAs Photocathodes

et al. 2019

Self Cite

View full text Add to dashboard Cite

A negative electron affinity photocathode based on GaAs nanopillar-array (NPA) Mie-type resonators is demonstrated and significant quantum efficiency enhancement is observed. Nanophotonic resonance assisted photoelectron emission into vacuum is investigated, indicating an enhanced density of optical states due to increased light concentration and increased electron emission area. For visible wavelengths, the Mie resonances in GaAs NPA reduce light reflectivity to less than 6% compared to a typical value >35% and result in maximum quantum efficiency 3.5 times greater than a GaAs wafer photocathode without the NPA structure. Comprehensive simulations and experimental studies are presented.

show abstract

Improved activation technique for preparing high-efficiency GaAs photocathodes

Cited by 26 publications

References 25 publications

Application of scanning focused X-ray imaging positioning technique in preparation of GaAs photocathodes

Application of scanning focused X-ray imaging positioning technique in preparation of GaAs photocathodes

Energy Bandgap Engineering of Transmission-Mode AlGaAs/GaAs Photocathode

Optical-Resonance-Enhanced Photoemission from Nanostructured GaAs Photocathodes

Contact Info

Product

Resources

About