Influence of light intensity on hole transport in a-Si:H transient photocurrents

Hole transport in transient photocurrent measurements for a-Si:H p-i-n structures has been investigated as a function of light intensity, bias voltage and temperature. One important result is that in comparison with electron transport, the space-charge-limited-current features do not appear, even at very high light intensity. Specifically: no current cusp and no obvious shift of extraction times with light intensity were observed. Analysis of the situation leads to the conclusion that the relatively low value of the hole mobility-lifetime product, caused by charge trapping in deep gap states, is the dominating factor in the loss of space-charge-limited-current aspects in hole transport.