Device level characterization for energy bandgap of strain-relaxed SiGe and oxide/SiGe barrier height

Abstract

From the interface state density with energy plot measured by capacitance-voltage characteristics, we have derived the energy bandgap of strain-relaxed Si1-xGex (x: 0.4 and 0.7) for the first time at the device level, because the allowed states increases sharply near the conduction and valence bandedges. We find that the energy bandgap of SiGe is reduced from 0.90 to 0.83 eV as the Ge composition increases from Si0.6Ge0.4 to Si0.3Ge0.7. In contrast, similar oxide/Si1-xGex conduction-band barrier heights of similar to3.1 eV have been obtained for both SiGe cases using Fowler-Nordheim tunneling. These results are in good agreement with published theoretical and experimental data from material level characterization. The device level characterization is especially important because the SiGe composition and material property may be altered after thermal cycles for device fabrication. (C) 2004 The Electrochemical Society.