Resolution characteristics of graded doping and graded composition transmission-mode AlGaAs/GaAs photocathodes

Abstract

The resolution model of a graded doping and graded composition transmission-mode AlGaAs/GaAs photocathode is solved numerically from the two-dimensional continuity equations. According to the model, we calculate the theoretical modulation transfer function (MTF) of different graded doping and graded composition structures. The simulation results show that both graded composition and graded doping structures can increase the resolution of the photocathode. The exponentially doping and linear composition photocathode has the maximum resolution among the possible graded doping and graded composition photocathodes. The resolution improvement is attributed to the built-in electric field induced by a graded composition or graded doping structure. The simulation results also show that the MTFs of AlGaAs/GaAs cathodes increase as the AlGaAs layer thickness decreases, or the incident light wavelength increases.

Theoretical analysis and modeling of photoemission characteristics of GaAs nanowire array photocathodes

“…Thus, these photocathodes have several important applications, including night vision image intensifiers, photo-multiplier tubes, polarized electron sources for next-generation electron accelerators, and electron beam lithography [1][2][3][4][5]. The quantum efficiency, electron spin polarization, stability, and reflectivity of GaAs film photocathodes have been widely investigated [6][7][8][9][10]. In the GaAs film photocathodes, the photoelectrons can only be emitted when they have been transported to the cathode surface.…”

Negative electron affinity GaAs wire-array photocathodes

“…Recently, with the rapid development of space detection, high-resolution night-vision imaging, next-generation electron accelerators, lowenergy electron microscopes, and electron beam lithography, an ever-pressing demand has arisen for photocathodes with higher sensitivity, wider spectral response range, higher emission current density, and higher spin polarization. Thus, some new GaAs-based photoemission material structures, such as graded doping/band-gap [6][7][8], strained [9], and superlattice structures [10][11][12], have been proposed to increase the quantum efficiency or spin polarization of GaAs-based photocathodes. However, all of these new photoemission materials rely on GaAs-based epitaxial thin films as the active layers of photocathodes.…”