Patent ID: 7872330

Claim:
A bipolar transistor, comprising: (a) an n-doped collector that includes a III-V semiconductor; (b) a p-doped base formed over the collector, wherein the base has a graded band gap, the grade of the base band gap being greater in a first region that is adjacent to the collector than in a second region, and wherein the average band gap of the first region is lower than the average band gap of the second region, wherein each of the first and second regions has a p-doping concentration in a range of between about 1.0×10 19 cm −3 and about 7×10 19 cm −3 , where a thickness of the first region is less than or equal to 25% of a total thickness of the base, and wherein the first region and the second region each include a III-V semiconductor; and (c) an n-doped emitter that includes a III-V semiconductor and is formed over the base, wherein said second region is adjacent to the emitter.