Reduction of Forward Bias Degradation in 4H-SiC PiN Diodes Fabricated on 4H-SiC Bonded Substrates

The advantage in reducing forward bias degradation of bipolar 4H-SiC devices using a 4H-SiC bonded substrate is demonstrated. To evaluate the differences in forward bias degradation between a 4H-SiC bonded substrate and a commercially available 4H-SiC bulk substrate, a forward current stress test and subsequent photoluminescence (PL) imaging of PiN diodes fabricated on both the substrates were performed. Unlike the bulk substrate, the bonded substrate maintained a low ΔVf and the variation among the measured diodes was extremely small even after applying the highest current density of 1500 A/cm2. The investigated number of bar-shaped SSFs within the electrically stressed diodes with more than 1000 A/cm2 revealed the possibility that the BPDs existing at deep positions below the epilayer/substrate interface were drastically reduced in the 4H-SiC bonded substrate.