Signal Readout in a-Si:H Pixel Detectors

Amorphous- or polysilicon thin-film technology can be used to make readout electronics for large-area a-Si:H pixel detectors. A switch consisting of two a-Si:H p-i-n diodes was studied to readout signals from pixels for the imaging of X-ray or gamma ray distributions. A charge storage time of 20 msec and a readout time of 0.7 μsec were achieved. For the detection of single ionizing particles, polysilicon thin-film-transistor amplifiers can be integrated to amplify the small signals at the pixel level before readout. Prototype polysilicon TFT amplifiers were designed and fabricated. The measured gain-bandwidth product was ~300 MHz and the input equivalent noise charge was ~1000 electrons for a 1 μsec shaping time.