Observation of two types of trapping centers in thin film transistors using charge pumping technique

Using voltage- and frequency-dependent charge pumping techniques, we observed two types of trapping centers with different densities, cross-sections, and trapped charges at the polysilicon-(TEOS) gate oxide interface in thin film transistors (TFT's). These observations can be explained in terms of nonuniform energetic or spatial distribution of the traps due to the channel polysilicon grain structure or related to the process-induced interface defects. Mechanisms are discussed.>