The　impact　of　the　three　state-of-the-art　germanium　(Ge)　profiles　(box,　trapezoid　and　triangular)　across　the　base　of　SiGe　heterojunction　bipolar　transistors　(HBTs)　under　the　condition　of　the　same　total　amount　of　Ge　on　the　temperature　dependence　of　current　gain　β　and　cut-off　frequency　f　T,　as　well　as　the　temperature　profile,　are　investigated.　It　can　be　found　that　although　the　β　of　HBT　with　a　box　Ge　profile　is　larger　than　that　of　the　others,　it　decreases　the　fastest　as　the　temperature　increases,　while　the　β　of　HBT　with　a　triangular　Ge　profile　is　smaller　than　that　of　the　others,　but　decreases　the　slowest　as　the　temperature　increases.　On　the　other　hand,　the　fT　of　HBT　with　a　trapezoid　Ge　profile　is　larger　than　that　of　the　others,　but　decreases　the　fastest　as　the　temperature　increases,　and　the　f　T　of　HBT　with　a　box　Ge　profile　is　smaller　than　that　of　the　others,　but　decreases　the　slowest　as　temperature　increases.　Furthermore,　the　peak　and　surface　temperature　difference　between　the　emitter　fingers　of　the　HBT　with　a　triangular　Ge　profile　is　higher　than　that　of　the　others.　Based　on　these　results,　a　novel　segmented　step　box　Ge　profile　is　proposed,　which　has　modest　β　and　fT,　and　trades　off　the　temperature　sensitivity　of　current　gain　and　cut-off　frequency,　and　the　temperature　profile　of　the　device.　©　2013　Chinese　Institute　of　Electronics.