In　this　article,　new　electro　thermal　characteristics　degradation　and　failure　mechanism　of　silicon　carbide　junction　barrier　Schottky　(SiC　JBS)　devices　with　different　die　attach　mate-rials　under　300　degrees　C　power　cycle　(PC)　stress　were　investigated　andfound　based　on　thermal　structure　function　and　failure　analysis.The　results　showed　that　the　electro　thermal　characteristics　(ther-mal　resistance,Rth　j-d,　andON-resistance,RON)were　consistent,which　were　different　in　that　decreased　first　and　then　increased　for　nano　silver,　but　increased　overall　for　alloy　solders　under　300　degrees　CPC,　both　strongly　related　to　the　evolution　of　porosity,　second-phase,　interface　cracks,　and　grain　size　in　the　die　attach　layer.However,　the　electrothermal　characteristics　were　affected　by　die　attach　evolution　to　varying　degrees　due　to　different　diffusion　mechanisms,　causing　different　failure　phenomena　(50,　1200,　and　4000　failure　cycles　for　high-lead,　Au-Ge　solder,　and　nanosilver,respectively).　Meanwhile,　the　reverse　leakage　current　(IR)and　break　down　voltage　(V-R)variations　mainly　depended　on　chip　interface　states,　including　the　Schottky　barrier　lowering　effect(induced　by　AlW　intermetallic　compound　(IMC)　and　large　cracksgenerated　at　the　Schottky　contact　metal　layer/chip　interface)and　electrons　and　holes　trapped　at　the　SiO2/4H-SiC　interfacein　the　termination　zone.　Finally,　this　article　discussed　three　failure　mechanisms　observed　in　devices　employing　three　die　attach　materials　under　300　degrees　C　PC