4H-Silicon Carbide (4H-SiC) bipolar PiN diode rectifiers demonstrated ultra-high breakdown voltage (VBR > 10 kV), high current handling capability (> 8 A), low reverse leakage current, and drift conductivity modulation, as compared to the well-developed 4H-SiC Schottky barrier diodes (SBDs). The concentration of the performance-limiting trap such as Z1/2 (EC – 0.67 eV) in the n-type 4H-SiC epilayer has been considerably reduced (< 5×1012 cm-3) in recent years. The PiN diode structure integrates double p-type layers (p and p+). The p-type 4H-SiC layer quality is sub-standard than the n-type. The periphery protection was realized by Al+ ion-implantation (p+). The ion-implantation-induced crystal defects introduce electrically active traps and affect the PiN diode characteristics via charge trapping. So, this work focuses on identifying the traps in the 4H-SiC PiN diodes by deep-level transient Fourier spectroscopy (DLTFS)