Attenuation performance of reflection-mode AlGaN photocathode under different preparation methods

Abstract

To research the attenuation performance of the AlGaN photocathode, three samples with the same structures grown by metalorganic chemical vapor deposition were activated with three different activation methods, which are called Cs-only, Cs-O, and Cs-O-Cs activation, respectively. The spectral responses and attenuated photocurrents of the three AlGaN photocathodes were measured. The results show that the Cs-O activated AlGaN photocathode exhibits the lowest attenuation speed in the first few hours, and the attenuation speed of the Cs-only activated one is fastest. After attenuating for 90 min, the attenuation photocurrent curve of the Cs-O-Cs activated sample is coincident with that of the Cs-O activated one. The main factor affecting the photocurrent attenuation is related to Cs atoms desorbed from the photocathode surface.

Influence of Al fraction on photoemission performance of AlGaN photocathode

“…Compare with the maximal photocurrent of the previous Cs/O alternating, the maximal photocurrent was not increased anymore at the final Cs/O alternating. Then the photocathode activation experiment was completed [6].…”

“…AlGaN-based solar-blind photodetectors with high solar rejection and high activity performance were demonstrated for a wide range of commercial and military applications, such as ozone layer monitoring, sterilization/detection of biological and chemical agents, flame detection/fire alarms, engine monitoring, secure intersatellite communication, and missile plume detection [3][4][5]. The AlGaN-photocathodebased image intensifier also has low noise ratio, high sensitivity, and high responsivity, and was one of the best devices used to make a high-performance UV detector [6,7]. A few studies have also been reported on transmission-mode AlGaN photocathodes.…”

The effect of surface cleaning on quantum efficiency in AlGaN photocathode

“…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.…”

“…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.…”

Photoemission performance of thin graded structure AlGaN photocathode

“…In addition, the image intensifier and vacuum photodiode based on an AlGaN photocathode has the distinctive characteristics of low dark current and high sensitivity [7,8]. However, the r-mode AlGaN photocathode has been reported in recent years, which is not suited to the solar-blind detector due to its thick emission layer and cut-off wavelength [9][10][11][12]. An r-mode AlGaN photocathode with a thin AlGaN emission layer, which could be used for the t-mode photocathode, has been rarely reported.…”