Abstract
We demonstrate that photoemission properties of p-type GaAs can be altered by surface acoustic waves (SAWs) generated on the GaAs surface due to dynamical piezoelectric fields of SAWs. Multiphysics simulations indicate that charge-carrier recombination is greatly reduced, and electron effective lifetime in p-doped GaAs may increase by a factor of 10× to 20×. It implies a significant increase, by a factor of 2× to 3×, of quantum efficiency (QE) for GaAs photoemission applications, like GaAs photocathodes. Conditions of different SAW wavelengths, swept SAW intensities, and varied incident photon energies were investigated. Essential steps in SAW device fabrication on a GaAs substrate are demonstrated, including deposition of an additional layer of ZnO for piezoelectric effect enhancement, measurements of current–voltage (I–V) characteristics of the SAW device, and ability to survive high-temperature annealing. Results obtained and reported in this study provide the potential and basis for future studies on building SAW-enhanced photocathodes, as well as other GaAs photoelectric applications.
Highlights
Photocathodes are used as a source of electrons for numerous applications that include photomultipliers, electron microscopes, and particles accelerators [1,2,3]
Note that ZnO in the center region was removed to expose the GaAs surface for illumination and photoemission, and for the deposition of negative electron affinity (NEA) coating in future study
Without changing the laser beam spot size on a photocathode surface provides higher beam brightness; Polarized electron sources for particle accelerators [3], where the proposed method of modifying electron dynamics can be combined with a distributed Bragg reflector method to increase light absorption [8] for high-intensity low-emittance beams for fundamental nuclear physics research [7]; Electron microscopy, for which electron beam emittance can be reduced for the same beam intensity due to reduced laser-spot size
Summary
Photocathodes are used as a source of electrons for numerous applications that include photomultipliers, electron microscopes, and particles accelerators [1,2,3]. This research was motivated by findings [9] that piezoelectric fields generated in GaAs by surface acoustic waves (SAWs) suppress recombination and lead to extended electron lifetimes in this system. This is achieved by using SAWs to periodically bend the energy bands and to spatially separate. Two of us [12] suggested earlier that suppression of charge-carrier recombination due to SAW may improve the performance of GaAs photocathodes In this case, the electrons and holes are spatially separated, the recombination is suppressed. All the work is completed for both a bulk GaAs structure and a thin film GaAs structure
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