Deep-level transient spectroscopy study on double implanted n+–p and p+–n 4H-SiC diodes

Planar $n^{+}\mathrm{–p}$ and $p^{+}\mathrm{–n}$ junction diodes, fabricated in 4H-SiC epitaxial layers using a double-implantation technology (a deep-range acceptor followed by a shallow-range donor implantation and vice versa), are characterized using capacitance deep-level transient spectroscopy (DLTS) to detect deep levels, which may influence device electrical performance. Either Al or B was used as the acceptor, while N or P was used as the donor, with all implants performed at 700 °C and annealed at 1600–1650 °C with an AlN protection cap. Different traps were observed for the various dopants, which are believed to be related to different impurity-defect complexes. A trap at ${\mathrm{\sim E}}_V\text{+0.51\hspace{0.05em}}\mathrm{eV}$ was observed in nitrogen-implanted samples, while an acceptor trap at ${\mathrm{\sim E}}_V\text{+0.28\hspace{0.05em}}\mathrm{eV}$ and a donor trap at ${\mathrm{\sim E}}_C\text{−0.42\hspace{0.05em}}\mathrm{eV}$ were observed in Al-implanted samples. A prominent boron-related D-center trap at ${\mathrm{\sim E}}_V\text{+0.63\hspace{0.05em}}\mathrm{eV}$ is seen in the DLTS spectra of B-implanted diodes. In diodes with implanted phosphorus, three traps at ${\mathrm{\sim E}}_V\text{+0.6\hspace{0.05em}}\mathrm{eV},$ $E_V\text{+0.7\hspace{0.05em}}\mathrm{eV},$ and $E_V\text{+0.92\hspace{0.05em}}\mathrm{eV},$ are seen, which are not observed for implantations of other species.