Optical-Resonance-Enhanced Photoemission from Nanostructured GaAs Photocathodes

Abstract

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.

Defect-Assisted Photoemission in the hBN and TMDs/hBN Heterostructures

“…Both of these factors contribute to the enhancement of electron-coherent features. , Therefore, the simultaneous realization of the small working area and emission angle to enhance electron coherence will be desirable . Many photocathode materials have been proposed, such as W­(ZrO), LaB 6 , carbon nanotubes, and semiconductor or dielectric materials. ,,− Recently, we proposed a new material for a photoemission source, hexagonal boron nitride (hBN), possessing both nanoscale bright intensity and a near-vertical photoemission angle by using a designed nanostructure under a ∼400 nm femtosecond laser . The hBN is a van der Waals material with a wide bandgap (∼6 eV) and a high refractive index (in-plane n > 2.1) from ultraviolet to near-infrared. − Nanoscale light localization can be realized with hBN planar waveguide modes excited from an etch ring slit under an ∼400 nm femtosecond laser.…”

Enhanced Collection Efficiency of Photoelectrons of Negative Electron Affinity AlGaN Heterojunction Nanorod Array Photocathodes

“…The reason for the huge difference between simulation results and experimental results is due to the large number of emitted photoelectrons that are absorbed secondarily by neighboring nanowires. 27 In this article, a photoemission model of the fieldassisted Al x Ga 1Àx N heterojunction nanorod array photocathode is proposed to alleviate the phenomenon of ''secondary absorption.'' 28 The influence of the built-in electric field intensity and the thickness of the sub-layer on quantum efficiency of the nanorod is analyzed.…”

Electronic properties of graded Ga 1‐x Al x N superlattice nanowires photocathode: First‐principles

“…2 Recently, NW arrays structures have been applied to photocathodes, compared with semiconductor planar photocathodes, which can provide high-performance outgoing electron streams for large-scale equipment, such as high-energy electron sources, ultraviolet detectors, and electron beam lithography. 3 In addition, the negative-electron affinity nanowire photocathode obtained by purification activation method exhibits better vacuum stability and longer lifetime. 4 Although the pure NW arrays photocathode improves the photoemission capability, due to the contradiction between spin polarization and quantum efficiency, the performance cannot achieve a stable and stable growth.…”

“…Nanostructures have more application possibilities than bulk materials due to their unique optoelectronic properties, 1 where nanowire (NW) arrays with excellent ‘light trapping’ and carrier migration characteristics have attracted increasing attention 2 . Recently, NW arrays structures have been applied to photocathodes, compared with semiconductor planar photocathodes, which can provide high‐performance outgoing electron streams for large‐scale equipment, such as high‐energy electron sources, ultraviolet detectors, and electron beam lithography 3 . In addition, the negative‐electron affinity nanowire photocathode obtained by purification activation method exhibits better vacuum stability and longer lifetime 4 …”