Abstract
Color centers in silicon carbide (SiC), such as the negative silicon vacancy (VSi−) 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 VSi− and VSiVC0 in equilibrium. We show that stable VSi− 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 VSi− 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.
Highlights
Point defects in wide-bandgap semiconductors can have both ground and excited states within the energy gap and, are luminescent centers or often called color centers
It can be judged from the diagram of energy levels in Fig. 1 that in irradiated n-type materials in the absence of the divacancy and C antisite–vacancy pair, VSi can be stable in the negative charge state if the Fermi level is located at its (0|-) level at ∼EV + 1.25 eV
Monitoring the charge state of dominant intrinsic defects in equilibrium using electron paramagnetic resonance (EPR) helps to determine the location of the Fermi level and reveals the conditions for achieving photostable VSi− and VSiVC0 PL emissions in n-type, high-purity semi-insulating (HPSI) and p-type 4H-silicon carbide (SiC) materials with different doping levels and defect concentrations
Summary
Point defects in wide-bandgap semiconductors can have both ground and excited states within the energy gap and, are luminescent centers or often called color centers. A recent simulation of the coherence time in more than 12 000 host compounds at natural isotopic abundance shows that SiC possesses the longest coherence times among widegap nonchalcogenides.2 These favorable optical and spin properties make color centers in diamond and SiC promising spin qubits for applications in quantum technologies.. Combining repumping with the electrical charge control using p-i-n or Schottky diodes has been shown to be a very effective way for controlling the charge state of the divacancy and the Si vacancy in SiC, allowing for fast switching between the bright and dark states This approach is difficult to be implemented, e.g., for quantum emitters embedded in photonic devices. The charge-state control of single VSi− and VSiVC0 emitters in pure p-type SiC epilayers by controlling the concentration of the C vacancy and in ultrapure SiC materials by optical repumping is discussed
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