Development of 10-W, 1.7- to 3.4-GHz, Linear Power Transistor.
Final technical rept. 15 Mar 72-15 Mar 73,
RCA SOLID STATE DIV SOMERVILLE NJ
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To meet the requirements of the contract a new transistor, the TA8758, was designed. This transistor uses the RCA overlay structure with metal grid, polycrystal silicon emitter protection, and emitter ballasting. To expedite the evaluation of technology and the development of microstrip circuits, however, the TA8407 transistor was used as the primary test vehicle. New diffusion processes were developed to improve f sub t and current handling. The first process uses boron-nitride base deposition and a phosphorus arsenic emitter diffusion. The second process uses a doped-oxide base diffusion source and a phosphorus arsenic emitter diffusion. These new diffusion processes give a base width of 0.10 micrometers or less with little base pushout. The new processes make possible the control of the narrow base width, and because of the reduction of bulk-crystal-lattice defects emitter efficiency and overall linear performance at 3.4 gigahertz has been greatly improved. Thermal scanning of double-cell TA8407s under DC bias conditions exposed a problem in sharing between cells. Heavy emitter ballasting Finger ballasting greatly improved the cell sharing ability of the device so that biasing up to 18 V collector voltage and I sub C 250 mA is feasible with the TA8407.
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