Carbon-beryllium combinationally doped semiconductor

A double heterojunction bipolar transistor comprising:

• a base layer of a semiconductor material doped with a combination of carbon and beryllium, a first sublayer of the base layer being doped substantially with beryllium and a second sublayer being doped substantially with carbon;
• a collector layer adjacent to a first side of the base layer;
• and
• an emitter layer adjacent to a second side of the base layer opposite to the first side,
• wherein the second sublayer of the base layer is adjacent to the emitter layer.

A method of making a combinationally doped semiconductor layer, the method comprising:

• growing a first sublayer of the combinationally doped semiconductor layer, the first sublayer being doped substantially with beryllium;
• and
• growing a second sublayer of the combinationally doped semiconductor layer, the second sublayer being doped substantially with carbon, the carbon-doped second semiconductor sublayer being grown disposed on the beryllium-doped first sublayer,
• wherein a semiconductor material of the first semiconductor sublayer and the second semiconductor sublayer comprise a III-V compound semiconductor, the combinationally doped semiconductor layer being a base layer of a heterojunction bipolar transistor.