Photoelectric transducer switchable to a high-resolution or high-sensitivity mode

Abstract

A photoelectric transducer having a photocell includes a compound semiconductor substrate in which a photodiode is doped by an impurity of a conductivity type opposite to that of the substrate. An enclosure region is formed by the same doping impurity as the photodiode, surrounding but spaced apart from the photodiode. A gate electrode is formed on a portion of an insulation layer, the latter formed all over the substrate surface, which extends between the photodiode and the enclosure region. The enclosure region is selectively connected, via a contact hole through the insulation layer and a first switch to ground level. The gate electrode is connected via a second switch to a predetermined voltage having the same polarity as the conductivity type of the substrate. In a high-resolution mode, the first switch is closed and the second switch is open, so that the grounded enclosure region prevents carriers generated in the substrate, between the photodiode and the enclosure region, from flowing into an adjacent cell. In a high-sensitivity mode, the first switch is opened and the second switch is closed, so that the gate voltage generates a channel which electrically connects the photodiode to the enclosure region; thus, the carriers generated within the enclosure are all gathered to the photodiode. The first and second switches may be fabricated on a second semiconductor substrate, arranged parallel to but spaced from the compound semiconductor substrate and electrically connected thereto via bumps.

Dependencies are inferred from the claim text.