| 摘要 |
PURPOSE:To decrease dark currents and to obtain high sensitivity even at a time of low illuminance, by providing a pnp junction type picture element and a barrier part, which discharges the excessive electric charge in the picture element, when a semiconductor substrate is made of, e.g., p-type Si. CONSTITUTION:A picture element 1 is formed by a p-type layer, whose conductivity type is the same as that of a substrate 100, and an n-type layer 13. A potential well is formed in the picture element 1. The electric charge in the well is trasferred in a perfect transfer mode. A barrier part 10 is formed by the p-type layer 12 and an n-type layer 14, and a potential well is formed. The impurity concentration of the n-type layer 14 is made thinner than that of the n-type layer 13. The potential beneath the barrier part 10 is made shallower than that of the potential beneath the picture element 1. Since the signal charge is accumulated in the picture element 1, the dark currents generated in an accumulating part 3 are discharged through an ICG gate 6. Therefore, the dark currents are not included in the signal component. Since the picture element 1 is formed with a perfect-depletion type picture element, the signal charge is quickly transferred from the picture element. Since the surface of the picture element 1 is covered with the P-type layer, the depletion layer in the picture element part does not reach an Si-SiO2 interface. The dark currents generated at the Si-SiO2 interface are suppressed to low values. |
