The　two-dimensional　temperature　profile　of　a　power　SiGe　HBT　with　traditional　uniform　emitter　finger　spacing　is　calculated,　which　shows　that　there　is　a　higher　temperature　in　the　central　region　of　the　device.　With　the　aid　of　the　theoretical　analysis,　an　optimized　structure　of　the　HBT　with　non-uniform　emitter　finger　spacing　is　presented.　The　peak　temperature　is　lowered　by　23.82　K,　and　the　thermal　resistance　is　also　improved　by　15.09%　compared　with　that　of　the　uniform　one.　The　improvements　above　are　ascribed　to　the　increasing　the　spacing　between　fingers,　and　hence　suppressing　the　heat　flow　from　adjacent　fingers　to　the　center　finger.　Based　on　the　analytical　results,　two　types　of　HBTs　with　uniform　emitter　finger　spacing　and　non-uniform　emitter　finger　spacing　are　fabricated　and　their　temperature　profiles　and　thermal　resistance　are　measured.　The　measured　results　agree　well　with　the　calculated　results,　verifying　the　accuracy　of　the　calculations.　For　the　HBT　with　non-uniform　emitter　finger　spacing,　the　peak　temperature　and　the　thermal　resistance　are　improved　markedly　over　a　wide　biasing　range　compared　with　that　of　the　uniform　one.　Therefore,　both　the　calculated　results　and　the　experimental　results　verify　that　the　optimized　structure　of　power　HBT　with　non-uniform　emitter　finger　spacing　is　superior　to　the　uniform　emitter　spacing　structure　for　enhancing　the　thermal　stability　of　power　devices　over　a　wide　biasing　range.　(C)　2009　Elsevier　Ltd.　All　rights　reserved.