Doping effect of oxygen or nitrogen impurity in hydrogenated amorphous silicon films

O, N, or C impurity was separately incorporated into a-Si:H films by hot-wall glow discharge decomposition. The effect of the impurity incorporation was investigated by electrical and electron spin resonance measurements. Both O and N impurities were found to increase the dark conductivity by decreasing its activation energy in a-Si:H films. Furthermore, it was found that O and N impurities delay the photoresponse. C impurity, however, has no appreciable effect on them. These findings suggest that O and N impurities shift the Fermi level upward and form a trapping state for photoexcited electrons, supporting our O+3 and N+4 model.