First-Principles Study of Proton Irradiated Color Centers in 4H-SiC

Optically active point defects in semiconductors are promising for quantum sensing close to room temperature and quantum communication at temperatures as low as ~4 K. One system that has shown great promise are point defects in 4H-SiC, including V⁰_Si,V⁰_C, and (V_C+V_Si)⁰. However, most current research uses optical excitations to control the spin states of these point defects, which generally lacks flexibility in controlling wavelength when trying to specifically excite different defects. Motivated by the success of single ion implantation, we aim to explore an alternate method to initialize/write these optically active defects via proton irradiation. Here we utilize real-time time-dependent density functional theory (RT-TDDFT) to examine the process of channeling protons exciting V⁰_Si,V⁰_C, and (V_C+V_Si)⁰ defect states in 4H-SiC. Specifically, we monitored the interaction between a proton with velocities of [1.0, 0.2, 0.15, 0.1, 0.05 a.u.] and vacancy defect states through electronic stopping power, occupation number of the Kohn-Sham states, and e-h pair count. From these simulations, we found the proton to be able to transfer its energy into the local electron density of the defect and excite each type of vacancy in 4H-SiC. Additionally, the amount of excitation varied based on the velocity of the proton and which defect state it was acting on, opening up the opportunity for enacting control over the excitation of each defect. Furthermore, similar to optical inversion, we found the proton to generate varying amounts of e-h pairs in the defect states depending on its velocity, which can potentially be used to control the charge state of each defect by locally changing the quasi-Fermi level. Last but not least, we note that the ion beam method might suffer from the fact that it takes longer for ions to travel in comparison to photons, which will give rise to slower writing speed.