Extension of the Constant Photocurrent method to determine densities of occupied and unoccupied localised states

C Main, S Reynolds, I Zrinscak, A Merazga

    Research output: Chapter in Book/Report/Conference proceedingChapter

    2 Citations (Scopus)

    Abstract

    This paper examines the use of Constant Photocurrent (CPM) measurements on thin film semiconductors, employing steady (DC) and modulated (AC) sub-gap illumination, to determine the density of localised states (DOS) in the bandgap. AC and DC measurements often result in different apparent absorption spectra. It is demonstrated that it is possible not only to extract information from the respective 'absorption' spectra, on the DOS below the Fermi level - i.e. occupied states, but also on the density of unoccupied states above the Fermi level. The ability to discriminate between these two groups of states by using DC and AC modulated sub-gap light arises from the frequency dependence of the different excitation pathways by which free electrons can be produced. AC modulated excitation will reveal absorption associated with transitions from occupied states into the conduction band, while DC excitation will include transitions from the valence band into unoccupied defect states, followed by slow thermal emission to the conduction band. We examine the temperature dependence of the CPM spectra and present a simple analysis of the DC and AC absorption spectra which allows the two regions of the DOS, above and below the Fermi level, to be determined.
    Original languageEnglish
    Title of host publicationAmorphous and Nanocrystalline Silicon Science and Technology- 2004
    Pages103-108
    Number of pages6
    Volume808
    DOIs
    Publication statusPublished - 2004

    Fingerprint Dive into the research topics of 'Extension of the Constant Photocurrent method to determine densities of occupied and unoccupied localised states'. Together they form a unique fingerprint.

  • Cite this

    Main, C., Reynolds, S., Zrinscak, I., & Merazga, A. (2004). Extension of the Constant Photocurrent method to determine densities of occupied and unoccupied localised states. In Amorphous and Nanocrystalline Silicon Science and Technology- 2004 (Vol. 808, pp. 103-108) https://doi.org/10.1557/PROC-808-A9.5