A high-sensitivity solid-state image sensor using a thin-film ZnSe-Zn_1-xCd_xTe heterojunction photosensor

Abstract

A high-sensitivity solid-state image sensor in which a charge-transfer device is overlaid by a thin-film photoconductor for the photosensor has been developed. The scanning registers are composed of interline transfer-type bucket-brigade registers (BBD) in the imaging area and charge-coupled registers (CCD) in the horizontal scanning circuit. The special feature of this device is that the thin-film photoconductor of ZnSe-Zn <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> Cd <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> Te heterojunction is directly formed not only on the Si-diode area but also on the scanning circuit area of BBD to obtain a high-aperture ratio. This solid-state image sensor has 506 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</sup> × 413 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</sup> picture elements and the imaging area is about 10.4 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</sup> × 13.5 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</sup> mm which corresponds to that of a 1-in vidicon. High sensitivity of 0.46 µA/lx (2856 K) and large blooming control capability have been obtained by this structure. The characteristics such as sensitivity, dark current, resolution, and blooming peculiar to the structure of a solid-state imager overlaid by a photoconductor are also discussed.