With　the　aid　of　a　two-dimensional　thermal-electrical　model,　the　thermal　stability　of　multi-finger　power　heterojunction　bipolar　transistors　(HBTs)　with　uniform　segmented　emitter,　and　non-uniform　segmented　emitter　are　studied.　It　shows　that　both　of　them　could　lower　the　peak　temperature　and　improve　the　non-uniformity　of　the　collector　current　density　distribution,　and　thus　improve　the　thermal　stability,　compared　with　an　HBT　which　has　traditional　non-segmented　emitter　structure.　At　the　same　time,　the　improvement　capability　of　thermal　stability　for　HBT　with　non-uniform　segmented　emitter　is　superior　to　that　of　HBT　with　uniform　segmented　emitter,　ascribing　to　selectively　divide　the　emitter　fingers　into　various　segments　according　to　the　difference　of　heat　dissipation　capability　in　emitter　fingers.　Furthermore,　the　improvement　capability　of　thermal　stability　for　HBT　with　non-uniform　segmented　emitter　is　enhanced　exponentially　as　segment　spacing　increases.　However,　for　HBT　with　uniform　segmented　emitter,　the　ability　is　less　sensitive　to　the　increasing　of　the　segment　spacing　as　it　exceeds　6μm.　Therefore,　the　technique　of　non-uniform　segmented　emitter　is　a　better　method　for　enhancing　the　thermal　stability　of　power　HBTs.　©　(2012)　Trans　Tech　Publications,　Switzerland.