Comparison of the photoemission behaviour between negative electron affinity GaAs and GaN photocathodes

Abstract

In view of the important application of GaAs and GaN photocathodes in electron sources, differences in photoemission behaviour, namely the activation process and quantum yield decay, between the two typical types of III-V compound photocathodes have been investigated using a multi-information measurement system. The activation experiment shows that a surface negative electron affinity state for the GaAs photocathode can be achieved by the necessary Cs-O two-step activation and by Cs activation alone for the GaN photocathode. In addition, a quantum yield decay experiment shows that the GaN photocathode exhibits better stability and a longer lifetime in a demountable vacuum system than the GaAs photocathode. The results mean that GaN photocathodes are more promising candidates for electron source emitter use in comparison with GaAs photocathodes.

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

“…Nevertheless, there exists a problem for GaN and AlGaN photocathodes, of which the photocurrent variation at the second activation stage is not very satisfactory. For GaAs and AlGaAs photocathodes, the photocurrent increases 4-5 times at the second activation stage, while it rises slightly for GaN and AlGaN photocathodes [7].…”

Physical origin of observed nonlinearities in Poly (1-naphthyl methacrylate): Using a single transistor—transistor logic modulated laser beam

“…In addition, it was used in two different techniques, the mode matched thermal lens [5,6] and the mode mismatched thermal lens spectropies. [7] It was used in a variety of applications such as scanning microscopy, [8] food analysis, and environmental research, [9,10] realization of optical logical gates, [11] measurements in microchips, [12] microchemical chips, [13] complex fluids, [14] investigation of the quantum yield, [15,16] ion chromatography, [17] and determination of iodine. [18] Changes in refractive index induced by an optical field can give rise to various nonlinear phenomena in optical materials.…”

Influence of wet chemical cleaning on quantum efficiency of GaN photocathode

“…GaN is a new type of semiconductor material with excellent characteristics of wide bandgap, low dielectric constant, corrosion resistance, high temperature resistance, and radiation resistance, so it is used widely in optoelectronic and microelectronic devices. [1][2][3][4][5][6][7] GaN-based photocathodes show good performance because of their high quantum efficiency (QE), low dark current, and concentrative emitting electron energy distribution. [8][9][10][11][12][13] Because of the wide bandgap (3.4 eV at room temperature), GaN photocathodes are naturally 'solar blind', and do not respond to visible light, so they have plenty of uses in the fields of ultraviolet detection, fire alarm technology, atmospheric monitoring, lithographic manufacture, and others.…”