Carbon antisite clusters in SiC: A possible pathway to theDIIcenter

Abstract

The photoluminescence center DII is a persistent intrinsic defect which is common in all SiC polytypes. Its fingerprints are the characteristic phonon replicas in luminescence spectra. We perform ab-initio calculations of vibrational spectra for various defect complexes and find that carbon antisite clusters exhibit vibrational modes in the frequency range of the DII spectrum. The clusters possess very high binding energies which guarantee their thermal stability-a known feature of the DII center. The dicarbon antisite (C2)Si (two carbon atoms sharing a silicon site) is an important building block of these clusters.

Structure and vibrational spectra of carbon clusters in SiC

“…The D II -center, with its rich vibrational spectrum located above the SiC phonon spectrum, is considered as a carbon-related defect. 2,3,5 Up to now, the complexity of the vibrational spectrum prevents an unambiguous identification of the microscopic structure. However, the theoretical investigations of the vibrational spectrum of small carbon clusters indicates that the dicarbon antisite (a carbon pair at the silicon site) is an important structural element of this defect.…”

“…Namely, the predicted high mobility of the carbon split-interstitials 9,10 should hinder the formation of D II centers at high temperatures 2,11 and opposes the thermal stability of the P−T centers. 6 Due to the high mobility, the carbon interstitials, which are a key ingredient of these centers, 2,5,6 should have vanished at elevated temperatures. Nevertheless, both features are observed experimentally.…”

“…Sofar, theoretical investigations focused on di-interstitials and small interstitial clusters at antisites. 5,8 A detailed discussion of the vibrational signature of larger clusters is still missing.…”

“…The analysis of further antisite-based clusters provides additional support for the previously suggested model of the dicarbon antisite as a core structure of the D II center. 5 The vibrational signature and the isotope shifts of the split-interstitial in the tilted configuration favor this defect as a candidate for the P−T centers, although an assignment to the dicarbon antisite cannot be completely rejected. The existence of LVMs up to 250 meV for compact antisite clusters shows that the original suggestion of a completely carbon-based U -center is possible.…”

Theoretical study of the mechanism of dry oxidation of4H-SiC

“…Figure 7 shows two such clusters, based on the bulk ͑C 3 ͒ Si defect proposed in Ref. 54. The occupied levels corresponding to the C v C double bonds are shifted towards ͓in the case of Fig.…”