Heterojunction bipolar transistors including an intrinsic base with an asymmetrical dopant depth profile

A method of forming a structure for a heterojunction bipolar transistor, the method comprising:

• forming a first terminal including a first semiconductor region on a first portion of a first semiconductor layer;
• forming a second terminal including a second semiconductor region on a second portion of the first semiconductor layer;
• forming an intrinsic base laterally disposed between the first terminal and the second terminal;
• and
• forming an extrinsic base on the intrinsic base,
• wherein the first semiconductor layer includes a third portion disposed between the first portion of the first semiconductor layer and the second portion of the first semiconductor layer, the intrinsic base includes a second semiconductor layer and a doped region in the third portion of the first semiconductor layer, the doped region has a dopant depth profile with a dopant concentration that is asymmetric between the first semiconductor region and the second semiconductor region, the second semiconductor layer is positioned between the extrinsic base and the third portion of the first semiconductor layer, and the second semiconductor layer has a thickness that varies as a function of position between the first semiconductor region and the second semiconductor region.