Threshold and saturation effects for photosignals in an amorphous silicon waveguide structure

Abstract

We report on a novel photosignal effect when laser light enters an amorphous hydrogenated silicon (a-Si:H) core waveguide and an external voltage is applied. Above a threshold voltage, the electric field separates the photocarriers in the a-Si:H layer so that the voltage across it is reduced. For larger voltages or high light intensities, this screening effect saturates. Analysis of the results yields electron and hole drift mobilities of 0.6 and 0.2 cm2/V s), respectively.