Off-resonant photoluminescence spectroscopy of high-optical quality single photon emitters in GaN

Abstract

In this work, we analyze the relevance of excitation parameters on the emission from single-photon emitting defect centers in GaN. We investigate the absorption spectrum of different emitters by photoluminescence excitation technique at 10 K. We report large spectral jumps (shifts up to 22 meV) in the emitters’ zero-phonon line (ZPL). The likelihood of such jumps is increased by the change in excitation energy. The shifts could indicate a large built-in dipole moment of the defects and suggest a possibility to electrically tune their ZPL in a wide range. From the photoluminescence excitation studies, we observe that for majority of the emitters the absorption peaks exist between 2 and 2.55 eV. The absorption peaks vary from emitter to emitter, and no universal absorption pattern is apparent. Finally, for selected emitters we observe significantly reduced spectral diffusion and instrument-limited linewidth of $138\mu \mathrm{eV}$ (0.04 nm). These findings show a new perspective for atomic defect GaN emitters as sources of coherent photons, shine new light on their energy level structure and show the possibility of tuning the ZPL, paving the way to fully harness their potential for applications in quantum technologies.