Charge pumping (CP) has been used to study defects in p-channel poly-c
rystalline silicon thin film transistors (TFTs). At high frequencies (
> similar to 1 kHz), we observe anomalous CP behavior in TFTs due to (
a) the high resistivity of, and/or slow electron trapping in, the poly
-Si channel and (b) the existence of a TFT drain offset region. At low
frequencies, the CP technique still appears to provide a useful measu
re of the TFT grain boundary defect density.