Method for fabrication of a heterojunction bipolar transistor

A method for fabricating a HBT, said method comprising steps of:

• forming a subcollector;
• depositing a medium-doped collector layer over said subcollector;
• depositing a P-type low-doped collector layer over said medium-doped collector layer;
• depositing a medium/high-doped collector layer over said P-type low-doped collector layer;
• growing a base over said medium/high-doped collector layer;
• depositing an emitter over said base.

A method for fabricating a HBT, said method comprising steps of:

• forming a subcollector;
• depositing a medium-doped collector layer over said subcollector, said medium-doped collector laver being uniformly doped;
• depositing a low-doped collector layer over said medium-doped collector layer;
• depositing a medium/low-doped collector layer over said low-doped collector layer;
• growing a base over said medium/low-doped collector layer;
• depositing an emitter over said base.

A method for fabricating a HBT, said method comprising steps of:

• forming a subcollector;
• fabricating a collector over said subcollector, said collector comprising a medium-doped collector layer adjacent to said subcollector, a low-doped collector layer over said medium-doped collector layer, and a medium/high-doped collector layer over said low-doped collector layer, said low-doped collector layer comprising GaAs doped with carbon at between approximately 1×1015 cm−3 and approximately 5×1015 cm−3, said medium/high-doped collector layer comprising GaAs doped with silicon at between approximately 2×1016 cm−3 and approximately 3×1018 cm−3, said medium/high-doped collector layer having a thickness between approximately 100 Angstroms and approximately 500 Angstroms;
• growing a base over said collector;
• depositing an emitter over said base.