Novel solid-state imaging devices with inherent MNOS memory gate

A novel solid-state imaging device with an inherent MNOS memory gate is proposed and writing and reading characteristics are discussed. To improve the writing of the low light inputs, a bias charge in addition to the signal charge is transferred into the MNOS memory Capacitor from a photodiode. Both enhanced writing and a Wide dynamic range are obtained under the following optimum bias condition: a preset photodiode voltage of 5 V, a memory pulse voltage of 35 V amplitude, and a 1-10 µs duration. Moreover, it was found that the stored charge signal could be nondestructively read from drain output under bias light, provided the drain voltage VDwas biased higher than the Surface potenteal φMGin the depletion layer below the memory gate. If VDMG, however, incoming light signals are detected regardless of shifts in the flat-band voltage optically induced during the Writing process. Finally, the reproduced images of readout and incoming light signals are demonstrated using a 5 × 5 2-D array.