Title :
Evaluation of the valence band discontinuity of Si/Si1-xGex/Si heterostructures by application of admittance spectroscopy to MOS capacitors
Author :
Takagi, Shin-ichi ; HOyt, Judy L. ; Rim, Kern ; Welser, Jeffrey J. ; Gibbons, James F.
Author_Institution :
Solid State Electron. Lab., Stanford Univ., CA, USA
fDate :
2/1/1998 12:00:00 AM
Abstract :
In this study, admittance spectroscopy is applied for the first time to MOS capacitors fabricated on Si/Si1-xGex/Si double-heterostructures, in order to evaluate the valence band discontinuity ΔEv at the Si/Si1-xGex interface. The principle of the measurement is presented and verified by the experimental results. A new feature of admittance spectroscopy applied to MOS capacitors is the ability to select the interface whose barrier is measured, by controlling the gate voltage. This fact is confirmed by the measurement of MOS capacitors, which include a SiGe well with different Ge contents at the front and the back interfaces. It is found from this measurement that, while ΔEv at the back interface of the double-heterostructure is measured under slight depletion conditions for MOS capacitors, ΔEv averaged between the front and the back interfaces is measured under accumulation conditions. The Gex content dependence of the measured ΔEv is found to be in fairly good agreement with the theoretical values
Keywords :
Fermi level; Ge-Si alloys; MOS capacitors; electric admittance measurement; elemental semiconductors; interface states; semiconductor heterojunctions; semiconductor materials; silicon; valence bands; MOS capacitors; Si-SiGe-Si; accumulation conditions; admittance spectroscopy; back interfaces; front interfaces; gate voltage; slight depletion conditions; valence band discontinuity; Admittance measurement; Current measurement; Energy measurement; Germanium silicon alloys; Loss measurement; MOS capacitors; Schottky diodes; Silicon germanium; Spectroscopy; Voltage control;
Journal_Title :
Electron Devices, IEEE Transactions on
