Spectral response characterization of a-Si: H-based MIS-type photosensors

This paper reports on a method and a test setup developed to measure the transient dark current and the spectral response characteristics of a-Si:H MIS photosensors. Using this method the segmented-gate/SiNx/a Si:H/n(+)/ITO structures have been characterized under different biasing conditions. The dependences of the dark and light signals on the refresh pulse amplitude, offset voltage and pulse width were measured and analyzed. It is found that the amplitude of the time-dependent component of the leakage current associated with charge trapping at the insulator-semiconductor interface can be significantly reduced by adjusting the offset voltage. The observed bias dependence of the spectral response characteristics is explained by analyzing the charge carrier transport in the absorption layer at different wavelengths of the incident light. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.