The effect of emitter layer variations on the current gain of AlGaAs-GaAs heterojunction bipolar transistors grown by chemical beam epitaxy
| Autor: | W.T. Moore, A.J. Springthorpe, S. Eicher, C.J. Miner, T.P. Lester, R.K. Surridge, J. Hu |
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| Rok vydání: | 1994 |
| Předmět: |
Materials science
business.industry Heterostructure-emitter bipolar transistor Transistor Bipolar junction transistor Analytical chemistry Heterojunction Semiconductor device Condensed Matter Physics Epitaxy Chemical beam epitaxy law.invention Inorganic Chemistry law Materials Chemistry Optoelectronics business Common emitter |
| Zdroj: | Journal of Crystal Growth. 136:230-234 |
| ISSN: | 0022-0248 |
| DOI: | 10.1016/0022-0248(94)90415-4 |
| Popis: | AlGaAs-GaAs heterojunction bipolar transistors have been fabricated with current gains > 200 for devices with emitter dimensions of 2×2 μm2. The epitaxial layers were grown using chemical beam epitaxy and were npn single heterojunction transistors with aluminum grading in the base. The high current gains observed in these devices are attributed to leaving a thin AlGaAs emitter layer (30–60 nm) over the entire base mesa and alloying through this layer to make base contact. This reduces the surface recombination currents to the extent that no significant decreases of current gain were observed with decreasing emitter size. Values of ft and fmax from 50–110 GHz were measured with fmax values dependent on the base doping which was in the (2−6) × 1019 cm-3 range. The epitaxial layers were grown on 3 inch diameter semi-insulating substrates in a VG Semicon 4200 CBE system. Room temperature photoluminescence intensities were used to determine the optimum growth conditions for both the n-Al0.3Ga0.7As emitters and the p-AlxGa1−xAs graded bases. SIMS, DCD X-ray diffraction, Hall effect measurements and photoreflectance were also used to evaluate the grown layers. Variations in emitter composition, doping and thickness were studied as well as the effects of growth interrupts at the emitter-base junction. Digital circuits that operate at data rates above 10 Gb/s> have been demonstrated. These include 4:1 multiplexers, 1:4 demultiplexers, dividers, preamplifiers and decision circuits. |
| Databáze: | OpenAIRE |
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