MECHANISMS AND DEVICE APPLICATIONS OF LIGHT-EMITTING PHENOMENA OF SI SI1-XGEX/SI QUANTUM-WELLS/

Photoluminescence (PL) intensity from SiGe mixed crystals was investig ated as a function of the growth temperature and/or atomic-hydrogen ir radiation rate during molecular beam epitaxy (MBE). As a result, a cle ar one-to-one correspondence between PL intensity and the surface segr egation length of Ge was obtained. This indicated that formation of Ge -Ge pairs during MBE is a key factor in determining PL intensity. Theo retical calculations showed that localized Si-Ge bonds cause s-like sy mmetry in the conduction band bottom and p-like symmetry in the valenc e band top. However, pairing of Ge-Ge atoms changes the local symmetry of the Si-Ge bonds and destroys the s-like symmetry in the conduction band. Such calculations explain the experimental results. This new kn owledge triggered the development of ''Ge-segregation-controlled MBE,' ' which successfully enhanced the PL intensity. Consequently, a prelim inary optoelectronic device, operating at 77 K with a light emitting d iode and detector on the same wafer, was fabricated. (C) 1998 American Vacuum Society.