Measurement of Spin-Polarized Photoemission from Wurtzite and Zinc-Blende Gallium Nitride Photocathodes

TL;DR

This study reports the first measurement of spin-polarized photoemission from wurtzite and zinc-blende GaN photocathodes, showing significant spin polarization levels and analyzing their underlying mechanisms.

Contribution

First experimental observation of spin-polarized photoemission from both wurtzite and zinc-blende GaN photocathodes with detailed analysis.

Findings

Peak spin polarization of 17% in wurtzite GaN

Peak spin polarization of 29% in zinc-blende GaN

Analysis of mechanisms influencing spin polarization

Abstract

Spin-polarized photoemission from wurtzite and zinc-blende gallium nitride (GaN) photocathodes has been observed and measured for the first time. The p-doped GaN photocathodes were epitaxially grown and activated to negative electron affinity (NEA) with a cesium monolayer deposited on their surfaces. A field-retarding Mott polarimeter was used to measure the spin-polarization of electrons photoemitted from the top of the valence band. A spectral scan with a tunable optical parametric amplifier (OPA) constructed to provide low-bandwidth light revealed peak spin polarizations of 17% and 29% in the wurtzite and zinc-blende photocathodes, respectively. Zinc-blende GaN results are analyzed with a spin-polarization model accounting for experimental parameters used in the measurements, while possible mechanisms influencing the obtained spin polarization values of wurtzite GaN are discussed.