Quenching of the luminescence intensity of GaN nanowires under electron beam exposure: Impact of C adsorption on the exciton lifetime

TL;DR

This study investigates how electron beam exposure causes luminescence quenching in GaN nanowires, highlighting the role of carbon adsorption in altering exciton recombination and efficiency.

Contribution

It reveals that carbon adsorption on GaN nanowires under electron irradiation affects both surface states and exciton dynamics, providing insight into luminescence degradation mechanisms.

Findings

Electron irradiation reduces luminescence efficiency.

Carbon adsorption creates new surface states affecting recombination.

Quenching depends on electron dose and surface chemistry.

Abstract

Electron irradiation of GaN nanowires in a scanning electron microscope strongly reduces their luminous efficiency as shown by cathodoluminescence imaging and spectroscopy. We demonstrate that this luminescence quenching originates from a combination of charge trapping at already existing surface states and the formation of new surface states induced by the adsorption of C on the nanowire sidewalls. The interplay of these effects leads to a complex temporal evolution of the quenching, which strongly depends on the incident electron dose per area. Time-resolved photoluminescence measurements on electron-irradiated samples reveal that the carbonaceous adlayer affects both the nonradiative and the radiative recombination dynamics.