Abstract
To test the effect of charged defect centres in a-Si: H we have performed drift-mobility measurements using a small-voltage-step technique in p-i-n and M-i-n samples already under strong forward bias. These measurements have been made as a function of forward bias and temperature. The drift mobility under double injection was of the order of one decade larger than that under single injection. The respective activation energies were approximately 0·13 and 0·17eV while the activation energies for the forward-bias currents were approximately 0·45 and 0·64 eV. We suggest that the differences in drift mobility are a result of an increase in the extended-state mobility arising from neutralization of the charge defects under double injection. which is not possible under single injection.