Internal photoemission technique for high-k oxide/semiconductor band offset determination: The influence of semiconductor bulk properties

A method for extracting energy band alignment of metal/high-k oxide/semiconductor structures from internal photoemission experiments is discussed by modeling the excitation and relaxation processes taking place in the semiconductor at photon irradiation. Classical literature data on photoemission of electrons from silicon and germanium surfaces into vacuum is compared with more recently published data on HfO
₂
/Si and HfO
₂
/Ge structures to identify characteristic features of photoelectric yield. We find that a dominating structure of such spectra, which often has been assumed to originate from the oxide barrier, derives from the energy dependence of absorption coefficient and mean free paths of excited electrons. Our results indicate that most IPE data on high-k oxide/silicon and germanium structures need re-interpretation.