Hetero-junction bipolar transistor and a method for manufacturing the same

A hetero-junction bipolar transistor comprising:

• a collector layer including an inner collector region with a first thickness and an outer collector region with a second thickness greater than the first thickness;
• an extrinsic base layer disposed on the collector layer of the outer collector region;
• an intrinsic base layer disposed on the extrinsic base layer in the outer collector region and on the collector layer in the inner collector region, the intrinsic base layer being made of a first semiconductor material with a first band gap energy;
• and
• an emitter layer made of a second semiconductor material with a second band gap energy greater than the first band gap energy, the emitter layer being disposed on the intrinsic base layer.