Monte Carlo Modeling of Spin-polarized Photoemission from p-doped GaAs Activated to Negative Electron Affinity

TL;DR

This paper uses Monte Carlo simulations to analyze the fundamental mechanisms affecting quantum efficiency and electron spin polarization in p-doped GaAs activated to negative electron affinity, aligning well with experimental data.

Contribution

It provides a detailed Monte Carlo model that explains the interplay of relaxation mechanisms and emission processes influencing QE and ESP in GaAs NEA photocathodes.

Findings

QE and ESP are governed by bulk relaxation and emission timing.

Model accurately reproduces experimental transport and emission data.

Behavior at room temperature explained by intrinsic relaxation processes.

Abstract

The anticorrelation between quantum efficiency (QE) and electron spin polarization (ESP) from a p-doped GaAs activated to negative electron affinity (NEA) is studied in detail using an ensemble Monte Carlo approach. The photoabsorption, momentum and spin relaxation during transport, and tunnelling of electrons through the surface potential barrier are modeled to identify fundamental mechanisms, which limit the efficiency of GaAs spin-polarized electron sources. In particular, we study the response of QE and ESP to various parameters such as the photoexcitation energy, doping density, and electron affinity level. Our modeling results for various transport and emission characteristics are in a good agreement with available experimental data. Our findings show that the behaviour of both QE and ESP at room temperature can be fully explained by the bulk relaxation mechanisms and the time which electrons spend in the material before being emitted.