ABSTRACTWe have developed a new amorphous silicon image sensor technology using a matrix array of amorphous silicon thin film transistors and photodiodes, where the amorphous silicon nip photodiode is fabricated on top of a thick insulating layer, on top of the thin film transistor array. We call this ‘diode on top’ technology or DOTTY. The active diode area can be as high as 93%, compared to 50% for our conventional photodiode-TFT technology. This leads to a higher signal to noise performance, which is important for medical X-ray applications.