Book contents
- Frontmatter
- Contents
- Preface
- 1 Introduction
- Part I Basic properties
- Part II Characterization techniques
- 6 Electrical characterization by Fermi-probe technique
- 7 Electrical characterization by thermal activation
- 8 Characterization of oxide/silicon energy band alignment: internal photoemission and X-ray photoelectron spectroscopy
- 9 Electron spin-based methods
- Part III Real MOS systems
- Index
- References
8 - Characterization of oxide/silicon energy band alignment: internal photoemission and X-ray photoelectron spectroscopy
from Part II - Characterization techniques
Published online by Cambridge University Press: 05 October 2014
- Frontmatter
- Contents
- Preface
- 1 Introduction
- Part I Basic properties
- Part II Characterization techniques
- 6 Electrical characterization by Fermi-probe technique
- 7 Electrical characterization by thermal activation
- 8 Characterization of oxide/silicon energy band alignment: internal photoemission and X-ray photoelectron spectroscopy
- 9 Electron spin-based methods
- Part III Real MOS systems
- Index
- References
Summary
Internal photoemission
Basic principles
Internal photoemission (IPE) measures the electric current generated by the optical excitation of charge carriers to energies exceeding an energy barrier in order to find the lowest photon energy needed for the process. This energy corresponds to the energy offset limiting carrier escape. Together with X-ray photon spectroscopy (XPS), described in Section 8.2, IPE has become an important method for the experimental determination of energy barrier heights in MOS systems (Afanas’ev and Stesmans, 2007; Afanas’ev, 2008).
The energy scales for thermal processes, discussed in earlier chapters, are to be considered as averages across particle ensembles motivating the introduction of thermodynamic concepts, for example Gibbs free energy, denoted G. Optical excitations, which are the basis of photoemission processes, take place between photons and specific eigenstates. Therefore, the energy quantities may differ from those of thermal processes and will be denoted E in this chapter.
The first theoretical treatment of this physical effect was developed by Fowler (1931) for the escape of electrons from a metal into vacuum. The method has been commonly used for establishing the work functions of metals and the heights of Schottky barriers, using various levels of complexity for the interpretation of measured data (Williams, 1970; Dalal, 1971; Engström et al., 1986). In a MOS structure, the alignments between energy bands of the oxide and the semiconductor and between the metal and the oxide can be measured using the same principle.
- Type
- Chapter
- Information
- The MOS System , pp. 196 - 220Publisher: Cambridge University PressPrint publication year: 2014