Degradation of Majority Carrier Conductions and Blocking Capabilities in 4H-SiC High Voltage Devices due to Basal Plane
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1069-D07-17
Degradation of Majority Carrier Conductions and Blocking Capabilities in 4H-SiC High Voltage Devices due to Basal Plane Dislocations Sei-Hyung Ryu1, Qingchun Zhang1, Husna Fatima1, Sarah Haney1, Robert Stahlbush2, and Anant Agarwal1 1 Cree, Inc, Durham, NC, 27703 2 Naval Research Laboratory, Washington, DC, 20375 ABSTRACT This paper presents the effect of recombination-induced stacking faults on the drift based forward conduction and leakage currents of high voltage 4H-SiC power devices. To show the effects, 10 kV 4H-SiC MPS (Merged PiN Schottky) diodes have been fabricated on a standard wafer and a low BPD (Basal Plane Dislocation) wafer, and their IV characteristics were evaluated before and after a forward bias stress, which resulted in minority carrier recombination and conductivity modulation in the drift epilayer of the diodes. After the stressing, the diode fabricated on standard wafer showed a significant increase in forward voltage drop, as well as a marked increase in leakage current, which were due to induction of stacking faults. The diode on the low BPD wafer showed very little change after the stress because the induction of stacking faults was minimized. Similar results were also observed on a 10 kV 4H-SiC DMOSFET. The results suggest that recombination-induced stacking faults are detrimental to all device types, and injection of minority carriers in majority carrier devices should be avoided at all times.
INTRODUCTION The effects of recombination-induced stacking faults (SFs) on forward conduction of 4HSiC PiN diodes have been extensively studied and published [1]. It was discovered that the basal plane dislocations (BPDs), mostly originated from the substrates, result in the formation of stacking faults in the drift epilayer, which behave as potential barriers that decreases the area available for the current flow [2,3]. It was also speculated that the SFs only affect the recombination-based conduction, and have negligible effects on drift based conduction or reverse leakage characteristics. However, this is not a reasonable speculation, and therefore, should be challenged, because induction of SFs in the drift layer can be equated to creation of defects in the high E-field drift region, which can cause increased leakage currents in the off-state. Also, it should be noted that a potential barrier can adversely affect majority carrier drift conduction as well. This effect of SFs on majority carrier devices was first reported on 10 kV 4H-SiC JBS diodes [4], then, on 10 kV 4HSiC DMOSFETs [5]. However, further studies are necessary to better understand the problem. So far, this has not been a problem for typical majority carrier devices because minority carrier injection was not utilized. However, with recent advances in 4H-SiC device technologies, several majority carrier devices that utilize minority carrier injection to further improve their performances, such as MPS diodes, power MOSFETs and JFETs with body diodes, emerged.
The recombination-induced SFs may not cause serious problems
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