Deep levels related to the carbon antisite–vacancy pair in 4H-SiC

Hiroki Nakane,Xuan Thang Trinh,Masashi Kato,Ivan G Ivanov,Yutaro Ohkouchi,Nguyen Tien Son,Takeshi Ohshima

doi:10.1063/5.0059953

Abstract

Photo-induced current transient spectroscopy (PICTS) and electron paramagnetic resonance (EPR) are used to study irradiation-induced defects in high-purity semi-insulating (HPSI) 4H-SiC. Several deep levels with the ionization energy ranging from 0.1 to ∼1.1 eV have been observed in irradiated and annealed samples by PICTS. Among these, two deep levels, labeled E370 and E700 at ∼0.72 and ∼1.07 eV below the conduction band, respectively, are detected after high-temperature annealing. The appearance and disappearance of these two deep levels and the EPR signal of the positive C antisite–vacancy pair (CSiVC+) in the sample annealed at 1000 and 1200 °C, respectively, are well correlated. Based on data from PICTS and EPR and the energies predicted by previous calculations for different charge states of dominant intrinsic defects, the E370 and E700 levels are suggested to be related to the charge transition levels (0|–) and (+|0), respectively, of the C antisite–vacancy pair. The activation energy of Ea ∼ 1.1 eV in commercial HPSI 4H-SiC materials is, therefore, reassigned to be related to the single donor (+|0) level of CSiVC.

Highlights

Based on data from Photo-induced current transient spectroscopy (PICTS) and electron paramagnetic resonance (EPR) and the energies predicted by previous calculations for different charge states of dominant intrinsic defects, the E370 and E700 levels are suggested to be related to the charge transition levels (0|–) and (+|0), respectively, of the C antisite–vacancy pair
EPR measures the whole sample including the highly doped n-type substrate. This problem can be overcome using thick freestanding epilayers, which allow a direct correlation between EPR and deep level transient spectroscopy (DLTS) as has been successfully used for identification of deep levels related to the C vacancy (VC) in the single positive (VC+)6 and double negative (VC2−) charge states
PICTS cannot distinguish the emission to the conduction or the valence band from deep levels, our assignment of the observed peaks to the previously reported DLTS levels is based on the activation energy Ea in both n- and p-type materials and their thermal stability

Summary

INTRODUCTION

Silicon carbide (SiC) is a mature wide bandgap semiconductor for high-power, high-frequency, and high-temperature devices. In the most common polytype, 4H-SiC, intrinsic defects, including vacancies and their associated complexes, are predicted to have their different charge states located within the bandgap. For most of these defects, their negative charge states locate in the upper half of the bandgap, acting as deep electron traps and have a strong influence on the electrical and optical properties of the material. EPR measures the whole sample including the highly doped n-type substrate This problem can be overcome using thick freestanding epilayers, which allow a direct correlation between EPR and DLTS as has been successfully used for identification of deep levels related to the C vacancy (VC) in the single positive (VC+) and double negative (VC2−) charge states.. With deep levels acting as efficient carrier compensation centers, intrinsic defects have been used for the creation of highpurity semi-insulating (HPSI) SiC substrates for high-frequency power devices.10–12 In such HPSI material with the Fermi level located near the middle of the bandgap, EPR can access different charge states of defects and has been used for the identification of intrinsic defects responsible for the SI-properties of the materials.. The assignment of these deep levels based on PICTS and EPR data is discussed

EXPERIMENTAL DETAILS

PICTS AND EPR RESULTS

DISCUSSION