Patent GB-1457792-A (GB)
Title: Semiconductor devices
IPC: H04N5/335
Filed: 1974-01-09
Abstract: 1457792 Semiconductor devices PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 9 Jan 1974 [25 Jan 1973] 00942/74 Heading H1K A radiation sensitive device, e.g. for a picture sensor or light-spot position detector, includes a row of p type surface zones 42-49 (Fig. 6) in an n type body, each zone constituting a discrete detector element and all the zones of the row being covered by a continuous insulating layer over which lies a common gate electrode 54 by means of which the zones 42-49 may be capacitively charged. An additional p type zone 50 is situated adjacent the row, and is so located relative to the gate electrode 54 that the application of a suitable potential to the gate electrode 54 will induce an inversion channel in the surface of the n type body adjoining the zone 50. The device is such that the application of a progressively increasing potential to the gate electrode 54 causes the zones 42-49 to be successively connected to the additional zone 50 by inversion channels, permitting element-by-element readout of electrical data corresponding to the inte-  grated intensity of radiation falling on the elements since charging occurred. In the preferred embodiments this is achieved by applying a potential gradient along the length of the gate electrode 54, via terminals 55 and 56, but the same effect may be obtained by providing progressively varying thickness or electrical permittivity of the insulating layer along the length of the row. In Fig. 6 the additional zone 50 is located alongside the entire length of the row, whereas in Fig. 1 if (4) is situated at one end of the row, successive read-out from the zones 5- 12 occurring as the inversion channel under gate electrode 15 spreads progressively along the row. In both these embodiments the additional zone 50, 4 carries an electrode 51, 13 from which readout may be effected across an earthed resistor. Fig. 1 shows an improvement, applicable with modification also to Fig. 6, consisting of a second gate electrode 24 and additional zone 22, identical to those associated with the row of zones 5-12. The two gate electrodes 15, 24 are connected at each end, and an electrode 23 on zone 22 is connected to a read-out resistor identical to that connected to electrode 13. This arrangement permits the derivation of a difference signal free of components associated with the growth of the inversion channels. When the invention is applied to a 2-dimensional array for a picture sensor the additional zones associated with all the rows are provided with a common gate electrode extending perpendicularly to the rows and operating in a manner analogous to that of the row gates to permit sequential read-out of image data from each row in turn. In modifications of the described embodiments the surface layer of the semiconductor body may contain lifetimereducing dopants or the conductivity type of the surface of zones 42-49, 5-12 may be inverted during the capacitance charging process. Semiconductor materials mentioned are Si, Ge and III-V compounds, materials for the insulating layer may be silicon oxide or nitride or aluminium oxide, and the gate electrodes may be of Al, polycrystalline Si or lead oxide. The semiconductor body may also contain other circuit elements, e.g. for picture signal amplification.