OPTICAL-PROPERTIES OF GE1-YCY ALLOYS

The Ge1-yCy semiconductor alloy system offers promise as a material fo r use in heterostructure devices based on Si as well as other material s. We have grown Ge1-yCy alloys by solid source molecular beam epitaxy on Si substrates. Layer thicknesses ranged from 0.01 to 3 mu m, and A uger electron spectroscopy and secondary ion mass spectrometry indicat ed C fractions up to 3 at. %. Optical absorption in the near-infrared region indicated a shift in the energy bandgap from that of Ge which w as attributed to the effects of alloying. The dependence of the bandga p on composition was consistent with linear interpolations of the Ge a nd C conduction band minimums. We observed a fundamental absorption ed ge characteristic of an indirect bandgap material. Photoluminescence s pectra at 11K of thick, relaxed layers indicated single broad peaks ne ar the expected bandgap energy.