Ligand hyperfine interactions at silicon vacancies in 4H-SiC

Abstract

become known to be very weak compared to the central line (CL) of this S = 3/2 center. Therefore, the V − Si center in hexagonal polytypes was believed to give rise to only one EPR line like the center in the cubic crystal 3C-SiC with no ZFS [3]. We refer to this defect as the no-ZFS V − Si center. Later optically detected magnetic resonance (ODMR) studies reported several ODMR centers with axial symmetry and small ZFS, labelled T V1a , T V2a , T V1b and T V2b , which were suggested to be related to the V1 and V2 photoluminescence (PL) lines at 1. 438 and 1.352 eV, respectively,. The absence of the CL in the ODMR spectra measured under resonant excitation led to the assignment of these centers to the isolated neutral Si vacancy (V 0 Si ) with spin S = 1 [4]. Two PL centers are expected for two possible configurations

Vibronic States and Their Effect on the Temperature and Strain Dependence of Silicon-Vacancy Qubits in4H-SiC

“…Because of Kramers degeneracy, only axial splitting with 2D is allowed between the ± 1 2 and ± 3 2 levels. The experimental values of the ZFS in the ground state are 5 and 70 MHz for V1 and V2 centers, respectively, which are relatively small values because of the small deviation from the quasitetrahedral symmetry of the spin density [11]. In striking contrast, the values are on the order of about 1 GHz in the excited state for both centers at cryogenic temperatures [8,12], with a strong temperature dependence for the V2 center between cryogenic temperature and room temperature [13].…”

Energy levels and charge state control of the carbon antisite-vacancy defect in 4H-SiC

“…Si at the hexagonal (h) and quasicubic (k) lattice sites of 4H-SiC, respectively. 30 The hf structures due to the interaction between the electron spin and the nuclear spin of a 13 C (I ¼ 1/2, natural abundance 1.1%) occupying one of the four nearest C neighbors of V C can be seen in the spectrum plotted with the intensity-extended scale.…”

Identification of silicon vacancy-related electron paramagnetic resonance centers in 4H SiC

“…Consequently, defect complexes consiting V Si (−) and another single defect denoted as X may be suitable candidates for this role where X is expected to act perturbatively on the electronic structure of V Si (−). In order to preserve the C 3v symmetry reported for all EPR centers [27] X should be located along the c-axis establishing axial V Si (−)-X complexes. Here we note that such defect models have already been proposed [23,25] following similar arguments.…”

“…II. Since EPR signatures of V Si (−)-h/k are observed in the corresponding experimental spectra [27], we calculated the formation and binding energies within the Fermi level region, where V Si (−)-h/k is stable, i.e. between the (0/−) and (−/2−) charge transition levels of V Si (−)-h/k.…”

“…Owing to the lattice structure of the 4H polytype, two different V Si (−) defects can be formed: one is located at a hexagonal lattice site labeled as V Si (−)-h and V Si (−)-k residing at a quasicubic site. In this way two different photoluminescence (PL) and EPR signals are expected, however, four V Si (−)-related EPR signals have been observed labeled as T 1va , T 2va , T 1vb , T 2vb [3,[23][24][25][26] and further two denoted as R 1 and R 2 which have been recently attributed to this family [27]. Common properties of these centers are the S = 3/2 ground state, the C 3v defect symmetry, the same isotropic g-value of 2.0029 [27] and the relatively small zero-field splittings (ZFS) characterized by the D tensor (cf.…”