Formation of the Z1,2 deep-level defects in 4H-SiC epitaxial layers: Evidence for nitrogen participation

Abstract

As-grown 4H-SiC epitaxial layers were investigated by deep-level transient spectroscopy to study the formation of the well-known Z1,2 defect with energy levels normally detected at about EC−0.7 eV. Chemical vapor deposition, applying various nitrogen-doping concentrations and C/Si ratios (1.2–3) in the gas phase, was used to prepare the samples. The Z1,2 defect concentration was observed to increase with the incorporated nitrogen concentration. The dependence was linear for medium C/Si ratios (1.5–2.5). The highest and lowest applied C/Si ratios (3 and 1.2) enhanced and suppressed the Z1,2 defect formation, respectively. This behavior tentatively suggests a complex of nitrogen with interstitial carbon atoms or, less probably, silicon vacancies. In particular, the correlation between the Z1,2 defect formation and the nitrogen incorporation was clearly shown in the present investigation, in contradiction to conclusions of other authors. Previously reported negative-U properties of the Z1,2 deep-level defects could be confirmed. A 1:1 relation between the concentrations of Z1 and Z2 was obtained for the present as-grown epitaxial layers.

Response of Ni/4H-SiC Schottky barrier diodes to alpha-particle irradiation at different fluences

“…It was observed that defect E 0.39 disappeared after leaving the sample at room temperature for a week, showing that the defect was not stable at room temperature. The deep level defects E 0.62 and E 0.65 have been previously reported to be defects composed of several energy levels commonly referred to as the Z 1 /Z 2 [16,[26][27][28][29].…”

Effect of Trap Levels and Defect Inhomogeneities on Carrier Transport in SiC Crystals and Radiation Detectors

“…Near the room temperature, a growth of the dark current occurs, which has thermal activation energy of about 0.63 eV. A level with similar activation energy was reported in [10]. It was attributed to carbon vacancy [5], carbon interstitialnitrogen complex, or silicon vacancy [10].…”

Development of Process Technologies for High-Performance MOS-Based SiC Power Switching Devices

“…Studies on effects of C/Si ratio on deep trap densities are not conclusive at this point. Some studies show that high C/Si ratio reduces the EH 6/7 and Z 1/2 trap densities [77,81,82], while other study indicates the other way [83]. The incorporation of the shallow B and Ti has shown to increase with increasing C/Si ratio, which has been explained in terms of site-competition principle sine both types of impurities are believed to occupy Si site [77].…”