Over the past decade, quantum photonics platforms aiming at harnessing the fundamental properties of single particles, such as quantum superposition and quantum entanglement, have flourished. In this context, single-photon emitters capable of operating at room temperature (RT) have garnered significant attention, as they hold a strong potential for enabling cost-efficient and scalable instruments for applications ranging from quantum cryptography to quantum sensing. Among investigated candidates, single-photon emitters (SPEs) based on the III-nitride (III-N) platform stand out as promising competitors, benefiting from a well-established semiconductor infrastructure originally developed for solid-state lighting applications.

RT single-photon emission has been demonstrated in III-N materials from quantum dots (QDs) and defect-related emitters. This thesis addresses both types of emitters, aiming to deepen our understanding of their optical properties through photoluminescence (PL) measurements performed on individual emitters and time-resolved spectroscopy performed on QD ensembles. The discussion presented here is structured into three independent chapters, each addressing complementary aspects of this thesis.

Initially, we examine the experimental challenges associated with the record of PL signal issued from point-like sources and discuss the inherent biases arising from the adopted excitation scheme. These observations are supplemented by simulations of the photon extraction efficiency and Fabry-Perot interference phenomena that emerge when investigating micrometer-thick layers.

Having established the necessary experimental foundations, we delve into the optical properties of GaN/AlN self-assembled (SA)QDs, starting with the unique influence of spectral diffusion (SD) on such polar structures and its indication of local defect concentrations. We then detail the PL response of high-energy QDs to variations in excitation power and temperature, comparing our results with phenomenological simulations of QD recombination dynamics. We further supplement the analysis by assessing the single-photon emission properties of excitonic lines between cryogenic and RT with a particular interest for the influence of biexciton PL on the single-photon purity. To complete our investigation of the QD recombination dynamics, we analyze time-resolved PL transients acquired on an ensemble of QDs with an emphasis on the exciton lifetime and multiexcitonic recombination processes. Confronting our results with prior findings, we finally investigate the influence of growth conditions on the optical properties of GaN/AlN SAQDs.

In the final chapter, we shift our focus to the investigation of defect-related RT SPEs in GaN. We begin by highlighting the methodology developed to address these randomly distributed emitters and discuss the various protocols established to characterize their optical signature, concentration, and spatial distribution. Our results are supplemented with second-order photon autocorrelation measurements to assess the potential of such emitters for RT applications. We conclude by presenting perspective statistics to assess the spectral and spatial distribution of these SPEs along with the in-plane orientation of the emitting dipole.