Charge state control of the silicon vacancy and divacancy in silicon carbide

Color centers in silicon carbide (SiC), such as the negative silicon vacancy (V-Si(-)) and neutral divacancy (VSiVC0), have recently been shown to be promising quantum bits (qubits) for a variety of applications in quantum communications and sensing. Considerable effort has been spent on improving the performance of these optical spin qubits, and the instability of their charge state is an important issue to be solved. Using electron paramagnetic resonance to monitor the charge state of dominant intrinsic defects in n-type, high-purity semi-insulating and p-type 4H-SiC, we reveal carrier compensation processes and the windows of the Fermi level that allow us to obtain stable V-Si(-) and VSiVC0 in equilibrium. We show that stable V-Si(-) and VSiVC0 ensembles can be obtained in n-type (p-type) via controlling the concentration of the Si vacancy (the C vacancy and the C antisite-vacancy pairs). The charge-state control of single V-Si(-) and VSiVC0 emitters is expected to be possible in pure p-type layers by controlling the concentration of the C vacancy. In ultrapure materials, optical repumping is required for charge state control of single emitters.Funding Agencies|Swedish Research CouncilSwedish Research CouncilEuropean Commission [VR 2016-04068, VR 2016-05362]; EU H2020 project QuanTELCO [862721]; Knut and Alice Wallenberg FoundationKnut & Alice Wallenberg Foundation [KAW 2018.0071]