J. Phys. Colloques
Volume 42, Numéro C4, Octobre 1981Proceedings of the Ninth International Conference on Amorphous and Liquid Semiconductors
|Page(s)||C4-597 - C4-600|
J. Phys. Colloques 42 (1981) C4-597-C4-600
DUAL LIGHT BEAM MODULATION OF PHOTOCARRIER LIFETIME IN INTRINSIC a-Si:HP.D. Persans1 and H. Fritzsche2
1 Exxon CRSL, P.O. Box 45, Linden, NJ 07036
2 James Franck Institute and Department of Physics, University of Chicago, Chicago, IL 60637, U.S.A.
We present dual beam photoconductivity measurements on intrinsic glow discharge a-Si : H. Several recombination effects have been isolated by varying the wavelength and chopping frequency of a secondary photon beam while pumping the sample with a primary beam of band gap photons and detecting the changes in the photoconductivity. For T < 200K infrared quenching of photoconductivity with a low energy threshold of ~0.6 eV is found. Above 250K a different infrared quenching process occurs with a low energy threshold of ~0.9 eV. At intermediate temperatures (200K < T < 250K) a new positive modulation signal is observed. Quenching results are interpreted in terms of optical excitation of electrons from the valence band into recombination centers with small electron capture coefficients. The positive modulation signal is attributed to an optical transition between localized gap states.