LIGHT-INDUCED-ESR STUDY OF UNDOPED AND N-DOPED HYDROGENATED AMORPHOUS-SILICON

We have measured the light-induced electron spin resonance (LESR) in undoped and N-doped hydrogenated amorphous silicon over a wide range of excitation intensities. By decomposing the LESR signal into a broad component, the neutral-dangling-bond component and a narrow component, we find that the density of neutral dangling bonds (D0) increases under illumination at 77 K in undoped samples in the annealed state and in N-doped samples in both the annealed and light-soaked states. No saturation of the D0 density is seen even at excitation intensities of about 700 mW/cm2. However, a decrease in the D0 density occurs in undoped samples in the light-soaked state at excitation intensities below about 10 mW/cm2. We show that the change of the D0 density under illumination at 77 K can be accounted for qualitatively with a model in which conversion takes place between dangling bonds in various charge states.