M center in 4 H -SiC is a carbon self-interstitial

Abstract

The list of semiconductor materials with spectroscopically fingerprinted self-interstitials is very short. M center in 4H-SiC, a bistable defect responsible for a family of electron traps, has been deprived of a model which could unveil its real importance for almost two decades. Using advanced first-principles calculations and junction spectroscopy, we demonstrate that the properties of M, including bistability, annealing, reconfiguration kinetics, and electronic levels, match those of the carbon self-interstitial. [Pre-print published in Physical Review B 103, L180102 (2021);

Formation of carbon interstitial-related defect levels by thermal injection of carbon into n-type 4H-SiC

“…Note that while the amplitude of E 0.38 increases with annealing time, that of the E 0.59 level is approximately the same for all annealed samples, suggesting a different microscopic origin of the defects behind the two signatures. Although the activation energy of E 0.59 matches the one found experimentally for the M 2 level (0.63 eV 24 ), it seems unlikely that they are identical, given their different peak emission temperatures (265 K for E 0.59 vs. typically 295 K for M 2 ).…”

“…Note that the activation energy and apparent electron capture cross section for the 170 K peak are similar to the values previously found on the M 1 level (E a = 0.42 eV, σ n = 6 × 10 −15 cm 2 ) 17 . Given the fact that the M center has previously been shown to originate from charge transition levels (CTLs) of the C i 24 , and taking into account that during the present experiment considerable amounts of carbon can be expected to be continuously driven into the uppermost regions of the epilayer, which suggests the presence of the C i defect, it is tempting to identify the trap emitting at 170 K with the M 1 level. However, the data presented in the further course of this manuscript casts doubt on this identification; therefore, we choose to adhere to the temporary label E 0.38 within this work.…”

M-Center in Neutron-Irradiated 4H-SiC

“…The presented results, using the neutron irradiation, are consistent with all previously obtained and reported results on metastable defects in 4H-SiC using the low electron energy irradiation, proton irradiation and ion implantation [1][2][3][4][5][6][7]. Moreover, these results are consistent with the first-principal calculations of M-center [8]. The presented data reconfirm the previously made assignment of the M center to the carbon interstitial.…”

“…To the best of our knowledge, this is the first time a metastable defect in 4H-SiC has been observed by L-DLTS. According to the modeling studies [8], the M 1 deep level is assigned to the carbon selfinterstitial (Ci) residing on the hexagonal lattice site (-h). If the S 1 emission lines splitting (S1 1 and S1 2 in Figure 4) corresponds to silicon vacancies (V Si ) residing on two different lattice sites, such as the carbon vacancy (V c ) [17], then we can assign two observed L-DLTS emission lines S1 1 and S1 2 to V Si residing on two lattices sites, cubic (-k) and hexagonal (-h), respectively, while the M 1 deep level resides on the hexagonal (-h) lattice site.…”

“…Recently, Coutinho et al [8] provided the direct evidence on the existence of the M 4 (0.86 eV) deep level in 4H-SiC. Combining the advanced first-principles calculations and isothermal DLTS, it was demonstrated that the properties of M-center, including bistability, annealing, reconfiguration kinetics and electronic levels, match those of the carbon self-interstitial.…”