SIGNAL READOUT IN A-SIH PIXEL DETECTORS

Amorphous- or polysilicon thin-film technology can be used to make rea dout electronics for large-area a-Si:H pixel detectors. A switch consi sting 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 s torage time of 20 msec and a readout time of 0.7 musec were achieved. For the detection of single ionizing particles, polysilicon thin-film- transistor amplifiers can be integrated to amplify the small signals a t the pixel level before readout. Prototype polysilicon TFT amplifiers were designed and fabricated. The measured gain-bandwidth product was approximately 300 MHz and the input equivalent noise charge was appro ximately 1000 electrons for a 1 musec shaping time.