Application to an Area Image Sensor

On the Si MOS-switching-FET matrix array, a-Si H is deposited by rf reactive sputtering in Ar and H2 atmosphere. This sputtered a-Si H is also used in vidicons (Imamura et al., 1980). Then the ITO common electrode is 

Since a-Si H has a high resistivity, the Al electrode array pitch determines the resolution for this device. One pixel area is 23.5 X 13.5 pm. The associated Al electrode is 20.5 X11 pm. Therefore the ratio between Al electrode area and one pixel area is as high as 0.73. 

The ITO electrode is negatively biased relative to the Al electrode. Electron and hole pairs are generated by the incident light and electrons pass through the a-Si H. Since in undoped a-Si H the electron mobility is small, nitrogen is added to the sputtering atmosphere to increase the electron mobility. As a result, the photocurrent saturation voltage for the photodiode decreased to 5 V and the photoresponse time decreased to less than 500 psec (Shimomoto et al., 1982). 

At high light intensity, the photocurrent discharges the Ca and Cd rapidly, and the potential difference between the Al electrode and the ITO electrode becomes equal to the open circuit voltage for th e a-Si H photodiode. In this 

In the large negative applied voltage, the collection efficiency is nearly equal to unity over the whole visible light region. The lag for this device is 3% after 50 msec and little bum-in is observed (Tsukuda et al., 1981). 

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