Charge state switching of the divacancy defect in 4H -SiC

Abstract

Optical charge state switching was previously observed in photoluminescence experiments for the divacancy defect in 4H-SiC. The participating dark charge state could not be identified with certainty. We use constrained DFT to investigate the mechanism of charge state conversion from the bright neutral charge state of the divacancy defect to the positive and negative charge states including corresponding recovery of the neutral charge state. While we can confirm that the positive charge state is dark, we do not find evidence that the negative charge state is dark.We compute similar absorption energies required for conversion of the neutral defect to both charge states. However, the formation of the positive charge state requires a series of excitations involving a 2-photon excitation, while the creation of the negative charge state is achieved through a single 2-photon process. Calculated absorption energies for the recovery of the neutral defect from the positive charge state fit the experimental value better than from the negative charge state. Defect formation energies as a function of the Fermi energy show a very small Fermi energy range in which the negative charge state is most stable, while the positive charge state exhibits a wide stability range. Overall, our computational results give more support to the identification of the dark charge state as the positive over the negative charge state in the mechanism of optical charge state switching.

Electrical and optical control of single spins integrated in scalable semiconductor devices

“…1B, inset) (32). The location in depth of the observed defects is consistent with isolation to the i-type layer, as expected from formation energy calculations (35) and the local Fermi level (36). This depth localization provides an alternative to delta-doping (37), which is not possible with intrinsic defects, facilitating positioning and control in fabricated devices ( Fig.…”

“…while it is less consistent with a recently proposed three-photon model converting to VV + (35,55). Further study of the spin dependence of this ionization may lead to the demonstration of spin-to-charge conversion in VV 0 .…”

Manipulating Single‐Photon Emission from Point Defects in Diamond and Silicon Carbide

“….0 2 ( R T ) [22] 637 [61] 10 6 [ 226] 0.1 [ 226] 3-5 0.04 [ 176] 0.4 [ 195] C S i V − 1.4-2.1 [82] 0.04 (4 K) [75] 738 [73] 10 6 [73] 0.1 [73] 70 [21] 0.37 [ 197] C G e V − 1.9-2.7 [82] 0.1 (5 K) [81] 602 [80] 0.05 [80] 70 [80] SiC V − Si 1.2-2.5 [ 41,42] 20 (17 K) [ 227] 858-916 [94] 10 4 [52] 0.25 [27] 6-9 [97] 3 [ 158] 26 [ 201] SiC [44] 64 (5 K) [ 117] 1078-1134 [84] 10 5 [56] 0.06 [56] 3-6 [56] 2.5 [28] SiC [45] 640-680 [87] 10 6 [87] 0.1 [87] h-BN 560-780 [ 132] 10 6 [ 228] 0.08 [ 229] 81 [ 134] 15 [ 185] 65 [ 202] WSe 2 730-750 [ 132] 0.12 [ 204] 21 [ 230] 18…”

“…These energy levels represent charge‐state transitions, where the defect may capture holes or electrons from the valence or conduction bands, respectively. Example point defects are shown for the case of 4H‐SiC in Figure a, including the Si vacancy (), [ 41,42 ] C vacancy (), [ 43 ] divacancy ( or VV), [ 44 ] C antisite‐vacancy pair (C or CAV), [ 45 ] nitrogen‐vacancy center (N or NV) [ 46 ] and vanadium impurity (V). [ 47,48 ]…”

Thermal evolution of silicon carbide electronic bands

“…cess may lead to a dark state, i.e., a permanent loss of qubits [33][34][35]. The qubit state can be restored by applying ∼1.3 eV optical excitation [33][34][35], where the nature of the dark state was debated in the literature [33,34,50]. According to one of the most recent study [35], the dark state can be identified as the negative charge state of divacancies where optical excitation at ∼1.25 eV is the threshold of photoionization of the electron from the ingap defect level to the conduction band edge at cryogenic temperatures.…”