INFLUENCE OF N, O AND C IMPURITIES IN A-SI-H

N, O and C atoms are separately incorporated in very pure a-Si:H. It is found that the addition of N or O increases the dark conductivity sigma-d, the photoconductivity sigma-p, the density of charged defects and the photocurrent decay constant, while the addition of C does not appreciably increases them. On the other hand, the addition of N or O of the amount of around 5 x 10(20) cm-3 gives rise to no change in the spin density increase by light-soaking, while the decrease in both sigma-d and sigma-p becomes more prominent. These results can well be explained if we assume that some of N and O atoms are incorporated in forms of N4+ and O3+ respectively.