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Development of a Planar Heterojunction Bipolar Transistor for Very High Speed Logic.
Final rept. 1 Oct 84-30 Jun 87,
CALIFORNIA UNIV SANTA BARBARA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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The following describes the results of research on III-V molecular beam epitaxial MBE growth, material characterization and the fabrication of heterostructure bipolar transistors HBT for very-high-speed logic applications. Work on the InGaPGaAs heterojunction HJ was completed. Isotype HJs were grown and evaluated by a CV reconstruction method in order to determine the energy band offsets. It was found that delta Ec 0.22 eV and delta Ev 0.24 eV for the lattice matched composition. An inverted AlGaAsGaAs HBT was investigated, and it was shown that an undoped, graded region between emitter and base would eliminate the conduction band spike and provide a buffer for Be diffusion. A new direction toward improvement in performance and fabrication techniques for the AlGaAsGaAs HBT was successfully demonstrated. Graded-bandgap nonalloyed ohmic contacts using n InAs for the AlGaAs emitter and p GaSb for the GaAs base were provided by selective epitaxial regrowth. The MBE growth conditions for grading from GaAs to InAs and GaAs to GaSb were determined. Low specific contact resistances were observed for both contact types. A self-aligned AlGaAsGaAs HBT with graded-gap contacts to both base and emitter was demonstrated.
APPROVED FOR PUBLIC RELEASE