Deterministic creation of optically active defects in AlN towards integrated single photon emitters*

Single photon emitters (SPEs) are fundamental building blocks for photonic-based quantum communication, quantum cryptography, and quantum computation. Recently, wide-bandgap compound semiconductor AlN has attracted great interest as potential host materials for SPEs due to room-temperature operation, strong second-order nonlinearity, and mature fabrication technology for photonic integrated circuits (PICs). Here, we report on deterministic creation of optically active defects in AlN toward monolithic integration of SPEs into AlN-on-sapphire PICs. In this work, we implant 7-Li⁺ ions in a periodic array into CVD AlN-on-sapphire with a pitch of 2 μm and 35 keV energy with ion fluences from 1x10¹⁶ - 1x10¹⁸ ions/cm² by focused ion beam. To achieve high dose a large beam limiting aperture is chosen and we measure the spot size to be 50 nm. The implant regions exhibit fluorescence after a subsequent annealing at 950 °C for 30 min in Ar environment. PL optical spectra at room temperature show broad emission between 700 and 800 nm, which has longer wavelength than PL from He broad-beam implanted AlN film (< 700 nm) [1]. Both PL spectra can originate from a point defect within AlN bandgap such as anti-site nitrogen vacancy complex (N_AlV_N) and divacancy (V_AlV_N), according to density functional theory calculation [2] or may be from an Li-based defect.

[1] Lu, Tsung-Ju, et al. "Bright high-purity quantum emitters in aluminum nitride integrated photonics." ACS Photonics 7.10 (2020): 2650-2657.

[2] Xue, Yongzhou, et al. "Single-photon emission from point defects in aluminum nitride films." The journal of physical chemistry letters 11.7 (2020): 2689-2694.