Si/SiGe/Si　HBTs　provide　excellent　microwave　power　performance　within　the　context　of　homo-junction　silicon　BJT.　Applications　of　the　technology,　however,　will　require　the　performance　specifications　with　regard　to　the　temperature　range　of　operation.　In　this　paper,　we　have　measured　the　temperature　dependence　of　properties　such　as　the　Gummel　plots,　ideality　factors,　the　base-emitter　voltage　VBE　at　various　base　current　levels,　current　gain,　common　emitter　characteristics　and　Early　voltage　from　23°C　to　260°C.　Our　data　show　the　current　gain　decreases　with　increasing　current　and　temperature　in　normal　operating　ranges,　and　that　the　variation　of　VBE　with　temperature　in　SiGe　HBT　is　smaller　than　that　of　homo-junction　silicon　BJT.　The　negative　differential　resistance　(NDR)　characteristics　of　Si/SiGe/Si　HBT　at　high　collector　-　emitter　voltage　and　high　current　is　observed　also.　These　are　important　in　preventing　thermal　runaway　in　power　transistors,　and　may　decrease　or　remove　the　necessity　of　emitter　ballast　resistors　and　provide　higher　power-added　efficiency　in　an　amplifier　block.　We　also　show　that　the　gain-Early　voltage　product　is　roughly　linear　with　1/T　above　ambient　temperature,　this　result　are　important　and　useful　for　circuit　applications.　©　2004　IEEE.