Mechanically and thermally stable Si-Ge films and heterojunction bipolar transistors grown by rapid thermal chemical vapor deposition at 900 °C

M. L. Green, B. E. Weir, D. Brasen, Y. F. Hsieh, G. Higashi, A. Feygenson, Leonard C Feldman, R. L. Headrick

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Traditional techniques for growing Si-Ge layers have centered around low-temperature growth methods such as molecular-beam epitaxy and ultrahigh vacuum chemical vapor deposition in order to achieve strain metastability and good growth control. Recognizing that metastable films are probably undesirable in state-of-the-art devices on the basis of reliability considerations, and that in general, crystal perfection increases with increasing deposition temperatures, we have grown mechanically stable Si-Ge films (i.e., films whose composition and thickness places them on or below the Matthews-Blakeslee mechanical equilibrium curve) at 900 °C by rapid thermal chemical vapor deposition. Although this limits the thickness and the Ge composition range, such films are exactly those required for high-speed heterojunction bipolar transistors and Si/Si-Ge superlattices, for example. The 900 °C films contain three orders of magnitude less oxygen than their limited reaction processing counterparts grown at 625 °C. The films are thermally stable as well, and do not interdiffuse more than about 20 Å after 950 °C for 20 min. Therefore, they can be processed with standard Si techniques. At 900 °C, the films exhibit growth rates of about 15-20 Å/s. We have also demonstrated the growth of graded layers of Si-Ge, and have determined that a strain gradient exists in these layers.

Original languageEnglish
Pages (from-to)745-751
Number of pages7
JournalJournal of Applied Physics
Issue number2
Publication statusPublished - 1991


ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

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