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An Experimental Evaluation of Modulated Photocurrent Spectroscopy as A Density of States Probe

Published online by Cambridge University Press:  15 February 2011

S. Reynolds ,
C. Main ,
D.P. Webb  and
M.J. Rose
S. Reynolds
Affiliation:
School of Science and Engineering, University of Abertay Dundee, Dundee DDI IHG, UK, s.reynolds@tay.ac.uk
C. Main
Affiliation:
School of Science and Engineering, University of Abertay Dundee, Dundee DDI IHG, UK, s.reynolds@tay.ac.uk
D.P. Webb
Affiliation:
Department of Electronic Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong.
M.J. Rose
Affiliation:
Department of APEME, University of Dundee, Dundee DD1 4HN, UK.
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Abstract

Modulated and Fourier-transformed transient photocurrent (MPC and TPC-FT) spectroscopies have been evaluated through a study of the density and capture properties of localised states in as-prepared and light-soaked PECVD a-Si:H samples over a range of temperatures and optical excitations. Both techniques return a conduction band tail state characteristic energy of approximately 22 meV. However, defect state spectra differ in detail and are strongly influenced by dc optical excitation. A feature correlating with the quasi-Fermi level position is observed, but the capture coefficient implied (of order 10-6 cm3 s-1) is some two orders greater than that calculated from thermal activation of emission frequencies. Such a value would suggest an implausibly low absolute density of defects. Possible explanations are briefly discussed and additional investigations proposed.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 557: Symposium A – Amorphous and Heterogeneous Silicon Thin Films—Fundamentals to Devices—1999 , 1999 , 427
Copyright
Copyright © Materials Research Society 1999

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