Mechanisms for Si dopant migration in molecular beam epitaxy AlxGa1−xAs
Because of well-known surface segregation effects in molecular beam epitaxy growth, Si dopant atoms deposited as thin layers in AlxGa1−xAs typically become distributed over many atomic layers. We have measured the Si depth distributions in (100) and (311)A samples grown at temperatures between 420 a...
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Veröffentlicht in: | Journal of applied physics 2000-10, Vol.88 (7), p.4056-4060 |
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Hauptverfasser: | , , , |
Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | Because of well-known surface segregation effects in molecular beam epitaxy growth, Si dopant atoms deposited as thin layers in AlxGa1−xAs typically become distributed over many atomic layers. We have measured the Si depth distributions in (100) and (311)A samples grown at temperatures between 420 and 655 °C, with Al fraction x=0, 0.1, and 0.32. The surface migration decay length Λ for a Si atom on a growing (100) surface is strongly temperature dependent but nearly independent of x, with Λ≈8 nm at 655 °C. The x=0(100) measurements show evidence for a minimum value Λ≈0.6 nm at low temperatures and a maximum value Λ≈8.5 nm at high temperatures. The data are in accord with a thermally activated surface segregation process with activation energy (1.8±0.4) eV acting in parallel with a temperature independent surface segregation mechanism. The (311)A surface shows Λ=(3.3±0.1) nm virtually independent of temperature for x=0. The Si decay length for the (311)A surface strongly increases with x, and for x=0.32 there is no significant difference in Λ for the (100) and (311)A surfaces. |
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ISSN: | 0021-8979 1089-7550 |
DOI: | 10.1063/1.1308073 |