Relationship between Phase Shift, Square-Wave Response and Density of States in Modulated Photocurrent Spectroscopy


Low- and high-frequency modulated photoconductivity measurements (LF and HF MPC) have been made on amorphous silicon films prepared by the expanding thermal plasma (ETP) and RF PECVD techniques. Time constants have been measured by decay of square wave excitation and behavior of complex frequency response. The influence of quasi-Fermi level position has been examined. Band tail slopes of 32 meV (ETP) and 37 meV (PECVD), and defect densities of order 1018 and 1017 cm-3 eV-1 respectively are found. Tail state capture coefficients of order 3×10-8 cm3 s-1 are calculated from overlapping LF and HF regimes. Defect state values for ETP (≤ 10-8 cm3 s-1) are smaller than for PECVD silicon films (≥ 10-7 cm3 s-1).

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  1. 1

    For a recent review see: J.P. Kleider, C. Longeaud and M.E. Gueunier J. Non-Cryst. Sol. 338–340, 390 (2004).

    Article  Google Scholar 

  2. 2

    R. Brüggemann, C. Main, J. Berkin and S. Reynolds, Phil. Mag B 62, 29 (1990).

    Article  Google Scholar 

  3. 3

    R.R. Koropecki, J.A. Schmidt and R. Arce, J. Appl. Phys. 91, 8965 (2002).

    CAS  Article  Google Scholar 

  4. 4

    W.M.M Kessels, R.J. Severens, A.H.M. Smets, B.A. Korevaar, G.J. Adriaenssens, D.C. Schram and M.C.M. van de Sanden, J. Appl. Phys. 89, 2404 (2001).

    CAS  Article  Google Scholar 

  5. 5

    S. Reynolds, C. Main, I. Zrinscak, Z. Aneva and D. Nesheva, Mat. Res. Soc. Symp. Proc. 762, A19.14.1 (2003).

    Google Scholar 

  6. 6

    S. Reynolds, C. Main, D.P. Webb and M.J. Rose, Phil. Mag. B 80, 547 (2000).

    CAS  Article  Google Scholar 

  7. 7

    C. Main, R. Brüggemann, D.P. Webb and S. Reynolds, Sol. St. Commun. 83, 401 (1992).

    CAS  Article  Google Scholar 

  8. 8

    K. Hattori, Y. Adachi, M. Anzai, H. Okamoto, Y. Hamakawa, J. Appl. Phys. 76, 2841 (1995).

    Article  Google Scholar 

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Reynolds, S., Main, C. Relationship between Phase Shift, Square-Wave Response and Density of States in Modulated Photocurrent Spectroscopy. MRS Online Proceedings Library 910, 901 (2005).

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