EVALUATION OF THE VALENCE-BAND DISCONTINUITY OF SI SI1-XGEX/SI HETEROSTRUCTURES BY APPLICATION OF ADMITTANCE SPECTROSCOPY TO MOS CAPACITORS/

In this study, admittance spectroscopy is applied for the first time t o MOS capacitors fabricated on Si/Si1-xGex/Si double-heterostructures, in order to evaluate the valence hand discontinuity Delta E-v at the Si/Si1-xGex interface. The principle of the measurement is presented a nd verified by the experimental results. A new feature of admittance s pectroscopy applied to MOS capacitors is the ability to select the int erface whose barrier is measured, by controlling the gate voltage. Thi s fact is confirmed bg the measurement of MOS capacitors, which includ e a SiGe well with different Ge contents at the front and the back int erfaces, It is found from this measurement that, while Delta E-v at th e back interface of the double-heterostructure is measured under sligh t depletion conditions for MOS capacitors, Delta E-v averaged between the front and the back interfaces is measured under accumulation condi tions. The Ge content dependence of the measured Delta E-v is found to be in fairly gored agreement with the theoretical values.