Optical and electrical properties of Si_1-x-yGe_xC_y thin films and devices

Si_1-x-yGe_xC_y thin films grown by low temperature chemical vapor deposition containing up to 1.2% substitutional C were incorporated into microelectronic devices. The chief aims are to demonstrate that the material is of suitable quality for device applications and to use the electrical and optical characteristics of the devices to study the material. Three sets of devices containing epitaxial Si_1-x-yGe_xC_y layers were fabricated and characterized. The temperature dependence of the collector current in Si_1-x-yGe_xC_y base heterojunction bipolar transistors indicated that the band gap of Si_1-x-yGe_xC_y increases + 26 meV %C^-1. Capacitance measurements on p⁺-Si_1-x-yGe_xC_y/p^--Si heterojunction internal photoemission structures indicated that the increase in band gap in the Si_1-x-yGe_xC_y is due primarily to downward movement of the valence band. Finally, Si_1-x-yGe_xC_y p-i-n diodes showed no degradation in reverse bias leakage compared with C-free devices for y < 0.01. However, the diodes did exhibit excess sub-band gap absorption which increased with [C].