Determination of defect densities by constant photocurrent method: Comparison of AC and DC methods

C Main, S Reynolds, I Zrinscak, Amar Merazga

    Research output: Chapter in Book/Report/Conference proceedingChapter (peer-reviewed)

    1 Citation (Scopus)

    Abstract

    We report on discrepancies in the absorption spectrum of a-Si:H measured by DC and AC constant photocurrent methods (CPM). Our measurements reveal discrepancies in the absorption coefficient alpha, of up to an order of magnitude. DC measurement gives the higher value for alpha at photon energies below the Urbach tail. In this paper we examine free carrier generation paths in AC CPM, and the influence of these paths on the photocurrent frequency response to modulated sub-gap illumination. A simple kinetic model is used to attempt to explain quantitatively the differences in the photocurrent frequency response for sub- and super-gap excitation. At first sight the basic AC technique is of doubtful validity, even at exciting frequencies as low as 1 Hz, since maintaining a constant AC photocurrent does not guarantee a constant carrier lifetime. On the other hand, the DC method involves several parallel excitation paths, obfuscating attempts to extract a density of states from the absorption spectrum. We demonstrate that a simple variation of AC CPM can provide a more accurate means of determining the density of states than DC CPM
    Original languageEnglish
    Title of host publicationAmorphous and nanocrystalline silicon-based films-2003
    EditorsJohn R. Abelson, Gautman Ganguly, Hideki Matsumura, John Robertson, Eric A. Schiff
    PublisherMaterials Research Society
    Pages131-136
    Number of pages6
    Volume762
    ISBN (Print)9781558996991
    Publication statusPublished - 2003
    Event2003 MRS Spring Meeting. Symposium on Amorphous and Nanocrystalline Silicon-Based Films - San Francisco, Ca., United States
    Duration: 22 Apr 200325 Apr 2003

    Publication series

    NameMRS Symposium Proceedings Series
    Volume762

    Conference

    Conference2003 MRS Spring Meeting. Symposium on Amorphous and Nanocrystalline Silicon-Based Films
    Country/TerritoryUnited States
    CitySan Francisco, Ca.
    Period22/04/0325/04/03

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