Silicon-germanium base heterojunction bipolar transistors bymolecular beam epitaxy |
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Authors: | Patton G.L. Iyer S.S. Delage S.L. Tiwari S. Stork J.M.C. |
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Affiliation: | IBM Thomas J. Watson Res. Center, Yorktown Heights, NY; |
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Abstract: | The devices were fabricated using molecular-beam epitaxy (MBE), low-temperature processing, and germanium concentrations of 0, 6%, and 12%. The transistors demonstrate current gain, and show the expected increase in collector current as a result of reduced bandgap due to Ge incorporation in the base. For a 1000-Å base device containing 12% Ge, a six-times increase in collector current was measured at room temperature, while a 1000-times increase was observed to 90 K. The temperature dependence of the collector current of the Si0.88Ge0.12 base transistor is consistent with a bandgap shrinkage in the base of 50 meV. For the homojunction transistors, base widths as thin as 800 Å were grown, corresponding to a neutral base width of no more than 400 Å |
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