Investigation of deep levels in n-type 4H-SiC epilayers irradiated with low-energy electrons

Deep levels in $n$ -type 4H-SiC epilayers have been investigated by deep level transient spectroscopy (DLTS). The ${\text{Z}}_{1∕2}$ and ${\text{EH}}_{6∕7}$ centers are dominant in as-grown samples. After electron irradiation at 116 keV, by which only carbon atoms may be displaced, the ${\text{Z}}_{1∕2}$ and ${\text{EH}}_{6∕7}$ concentrations are significantly increased. The ${\text{Z}}_{1∕2}$ and ${\text{EH}}_{6∕7}$ centers are stable up to $1500–1600°\text{C}$ and their concentrations are decreased by annealing at $1600–1700°\text{C}$ . In the irradiated samples, the trap concentrations of the ${\text{Z}}_{1∕2}$ and ${\text{EH}}_{6∕7}$ centers are increased with the 0.7 power of the electron fluence. The concentrations of the ${\text{Z}}_{1∕2}$ and ${\text{EH}}_{6∕7}$ centers are very close to each other in all kinds of samples, as-grown, as-irradiated, and annealed ones, even though the condition of growth, irradiation (energy and fluence), and annealing has been changed. This result suggests that both ${\text{Z}}_{1∕2}$ and ${\text{EH}}_{6∕7}$ centers microscopically contain the same defect such as a carbon vacancy.