PC-Mon-P8 - Optical and structural characterisation of colour centres in (PVT and PVD synthesized) AlN for quantum applications.

2. Physics and characterization
Amy Albrecht¹ , Jan Beyer¹, Christian Röder², Gleb Lukin², Andreas Lesnik², Sven Besendörfer², Sèbastien Pezzagna³, Tobias Lühmann³, Marius Wetzel², Muhammad Shaheer Khan¹, Johannes Heitmann¹, Jan Meijer^3
1 TU Bergakademie Freiberg, Institute of Applied Physics, D-09599 Freiberg, Germany
² Fraunhofer Institute for Integrated Systems and Device Technology IISB, D-91058 Erlangen, Germany
³ Applied Quantum Systems, Felix-Bloch Institute for Solid-State Physics, University Leipzig, D-04103 Leipzig, Germany

Abstract text
Colour centres in wide bandgap materials such as AlN are of growing interest for quantum applications, including qubits, single-photon sources and sensing. Density functional theory (DFT) calculations show that transition metals in combination with vacancy defects form promising colour centres within the bandgap of AlN, potentially forming a triplet ground state [1]. Experimental studies provide promising evidence for the single-photon behaviour of different defect species in AlN [2; 3].
This study presents the optical characterisation of AlN as a host for colour centres on differently grown AlN samples. Wafers from single crystals grown by PVT [4] were investigated with respect to as-grown PL activity and characteristic PL spectra after implantation and annealing. A correlation between the atomic mass of the implanted elements and the increase in PL intensity in the wavelength range 590-620 nm can be observed. This indicates an increase in optically active intrinsic defects (vacancies and vacancy complexes with oxygen), especially when lighter elements were implanted.
AlN films grown on sapphire and silicon substrates by RF magnetron sputtering at different temperatures were investigated for PL activity and film quality.
Optical characterisation was performed using PL and confocal µ-PL. Raman spectroscopy was employed to reveal strain for different regions of the samples whereas XRD measurements revealed structural information for the different growth conditions. From the structural analysis, a correlation between film quality, deposition temperatures and substrate material can be observed. Confocal microscopy images and AFM provide insight into the morphology.

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[2]  S. G. Bishop, et al., ACS photonics 2020, 7, 1636–1641.
[3]  J. K. Cannon, et al., Applied Physics Letters 2023, 122, 1721041–1721044.
[4]  T. Wicht, et al., Journal of Applied crystallography 2020, 53, 1080–1086.