Multiphoton Femtosecond Emission of Spin-Polarized Electrons from GaAs Sources*

A comprehensive study of multiphoton electron emission from various GaAs

microstructures has been carried out. These sources forgo using the conventional

GaAs negative electron affinity (NEA) surface activation as originally described

in Pierce and Meier (1976) where a photocathode source of spin polarized elec-

trons was first observed. [1] Instead, a pulsed 800 nm laser induces electron

emission through multiphoton absorption after electrons absorb enough pho-

tons to overcome the electron affinity of the GaAs (≈ 4 eV). This work is based

on previous results from our group where spin polarized electron emission from

non-NEA GaAs shards was observed using a pulsed light source. [2] The work

presented here reports on a comprehensive study of this type of photoemitter

with examination of the type of dopant used in the semiconductor source, pho-

toemission enhancement from Cs adsorption, and changes to the photoemitter

geometry that enhance the photoemitted intensity and its stability.

[1] Pierce, Daniel T., and Felix Meier. Phys. Rev. B, 13, 5484-5500 (1976)

[2] Brunkow et al. Appl. Phys. Lett., 114, 073502 (2019)