Effects of secondary laser illumination during the transient measurement in optical and electrical deep level transient spectroscopy

To separate the majority and minority carriers in the deep level transient spectroscopy (DLTS), the transient is usually measured in the dark. However, under some circumstances, the transient measurement should be performed under illumination. In these cases, the effects introduced by the illumination become a concern. In this letter, effects of secondary laser illumination on samples of hydrogenated amorphous silicon (a-Si:H) during the transient measurement in optical and electrical DLTS are reported. The experimental results show that background illumination decreases the time constant of the transient but it is unlikely to create new gap states during the short time period.