The non-radiative efficiency nnrhas been directly measured in hydrogenated amorphous silicon using photo-pyroelectric spectroscopy, for photon energies ranging from 1-5 to 2-2 eV at room temperature. The non-radiative efficiency is fairly constant for above-bandgap illumination, but displays a sharp minimum for photon energies near the bandgap energy. nnrincreases with sub-bandgap illumination, saturating at a value roughly one half as large as its high-energy value.
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We gratefully thank C. C. Tsai of the Xerox Palo Alto Research Center for the glow-discharge a-Si : H samples, J. Shinar of Iowa State University for the r.f. sputtered films and H. Fritzsche, S. Gu and J. Hautala for helpful discussions. This research was supported by the University of Minnesota, and by a McKnight-Land Grant award.