A proposed collector design of double heterojunction bipolar transistors for power applications

A new collector design for the AlGaAs-GaAs double heterostructure bipolar transistor (DHBT) is proposed, analyzed, and simulated. The base-collector junction is linearly graded and terminated with a highly doped thin layer to offset the adverse alloy grading electric field. Simple analytical formulas are derived to facilitate the implementation of the design. A proof-of-principle simulation has been carried out for an X-band AlGaAs-GaAs power DHBT to confirm the design and the derived formula. The simulation shows the breakdown voltage can be increased from 30 V to about 45 V while the critical current density is about the same. It is also shown that, unlike other refined DHBT structures, the proposed structure does not require critical control in the fabrication of the base-collector junction.<
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