A field effect controlled storage display device using polycrystalline silicon film

Abstract

A design analysis of a field effect controlled storage display tube was carried out. The analysis indicates that the semiconducting field effect layer should optimally have a resistivity greater than or equal to 106 Ω cm and be operated in the enhancement mode. Writing speeds of 106cm/sec should be feasible provided that the surface state densities do not exceed 1011/cm2 and the mobility is at least 0.1 cm2/Vsec. A feasibility study was carried out using thin polycrystalline silicon films as the field effect layer for this device. The silicon films were deposited by silane pyrolysis at 650°C on SiO2. Field effect measurements on a one micron thick poly-Si film showed a surface state density of 5 × 1011/cm2 and a field effect mobility of 0.1 cm2/Vsec. Small area phototype devices were fabricated and evaluated by corona charging of the Si02 surface. The device was found to turn on at 50 volts of either polarity with the off state near zero volts. When this field effect layer was placed on a ZnS electroluminescent phosphor layer, a contrast of 6 to 1 and a maximum brightness of 9.4 ft-L was obtained using a driving voltage of 600 V (8 KHz) on the interdigitating electrode structure. © 1973 American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.