Optical Dipole Structure and Orientation of GaN Defect Single-Photon Emitters

TL;DR

This study investigates the optical dipole structures and orientations of defect single-photon emitters in GaN using defocused imaging, revealing their dipole orientation and distribution related to crystal bonds, aiding understanding of their nature.

Contribution

The paper introduces a method to determine the 3D orientation of defect emitters in GaN and uncovers their dipole alignment relative to crystal bonds, advancing knowledge of their origin.

Findings

Emitters have a single dipole oriented nearly perpendicular to the c-axis.

Dipole orientations cluster around angles matching Ga-N bonds and Ga-Ga/N-N directions.

In-plane angular distribution is consistent across different emission wavelengths.

Abstract

GaN has recently been shown to host bright, photostable, defect single photon emitters in the 600-700 nm wavelength range that are promising for quantum applications. The nature and origin of these defect emitters remain elusive. In this work, we study the optical dipole structures and orientations of these defect emitters using the defocused imaging technique. In this technique, the far-field radiation pattern of an emitter in the Fourier plane is imaged to obtain information about the structure of the optical dipole moment and its orientation in 3D. Our experimental results, backed by numerical simulations, show that these defect emitters in GaN exhibit a single dipole moment that is oriented almost perpendicular to the wurtzite crystal c-axis. Data collected from many different emitters shows that the angular orientation of the dipole moment in the plane perpendicular to the c-axis exhibits a distribution that shows peaks centered at the angles corresponding to the nearest Ga-N bonds and also at the angles corresponding to the nearest Ga-Ga (or N-N) directions. Moreover, the in-plane angular distribution shows little difference among defect emitters with different emission wavelengths in the 600-700 nm range. Our work sheds light on the nature and origin of these GaN defect emitters.