Optical Dipole Structure and Orientation of GaN Defect Single Photon Emitters

Defect-based single-photon emitters play an important role in quantum information technologies. The study of quantum emitters in technologically mature wide bandgap semiconductors, such as the wide bandgap nitrides, is attractive for photonic integration. GaN has recently been shown to host very bright defect single photon emitters in the 600-700 nm wavelength range but very little is known thus far about their structure and origin [1,2]. We study these emitters in HVPE grown Wurtzite GaN epitaxial layers using the method of defocused imaging whereby the radiation pattern in the Fourier plane is recorded. This techniques enables the detection of the far-field emission pattern and the orientation of the optical dipole moment. Our experimental results show the defect emitters around 680 nm wavelength have dipoles oriented almost parallel to the crystal c-axis. Our results call into question the view that these defect emitters are related to crystal dislocations [2] and show that different emitters exhibit different characteristics. The measured optical dipole orientations suggest that these defect emitters could be substitute impurity atoms or complexes with dipole orientations along the Ga-N bonds and involve small lattice distortions. We will discuss the nature of GaN defect emitters in the light of our measurements. [1] arXiv:2206.12636 (2022), [2] Adv. Mat. 29, 1605092 (2017).