Non-Micropipe Dislocations in 4H-SiC Devices: Electrical Properties and Device Technology Implications
Materials Research Society Symposium Proceedings
Itiswell-known thatSiC wafer quality deficiencies aredelayingtherealization of outstandingly superior4H-SiC power electronics. While efforts to date have centeredon eradicating micropipos (i.e.,hollow core super-screw dislocations with Burgers vectors > 2c), 4H-SiC wafers and epilayersalsocontain elementary screw dislocations (i.e., Burgers vector = lc with no hollow core) in densities on the order of thousands per cm 2,nearly 100-foldmicropipe densities. While not nearlyas detrimentalto SiC
... etrimentalto SiC device performance as micropipes,ithas been previouslyshown thatdiodescontainingelementary screw dislocations exhibita 5% to 35% reductionin breakdown voltage,higherpre-breakdown reverseleakagecurrent,softerreverse breakdown I-V knee, and concentrated microplasrnic breakdown current filaments when measured under 13(2 testing conditions.This paper details the impact of elementary screw dislocations on the experimentally observed reverse-breakdown pulse-failure characteristics of low-voltage(< 250 V) small-area(< 5 4 2 + x 10 cm ) 4H-SiC p n diodes.The presenceof elementary screw dislocations did not significantly affectthe failurepropertiesof these diodes when subjectedto non-adiabaticbreakdown-bias pulsewidths ranging from 0.1 Itsto 20 lasin duration.Diodes with and without elementary screw dislocations exhibitedpositivetemperaturecoefficient of breakdown voltage and high junction failure power densitieswell above the failure power densities exhibitedby highly reliable silicon power rectifiers. This preliminaryresult, based on measurements from one wafer of SiC diodes, suggests thathighly reliable low-voltageSiC rectifiers may be attainable despitethe presence of elementary screw dislocations.