Charge transfer device

TLDR: In this article, the authors proposed a method to improve the imperfect transfer efficiency of the BBD by a method wherein the concentration of drains is lowered particularly than as in the past, and dependence upon a voltage of a drain and source current of the MOSFET is reduced.

Abstract: PURPOSE:To improve the imperfect transfer efficiency of the BBD by a method wherein the concentration of drains is lowered particularly than as in the past, and dependence upon a voltage of a drain and source current of the MOSFET is reduced. CONSTITUTION:When the concentration at the channel part of a P type substrate is designated as nA, and concentration at the N type drain 28 is designated as nD, and when nD becomes to the 10 times or more of nA, reduction of width WP of a depletion layer to extend to the substrate side becomes to a little, and when nD is made as the same grade or less with nA, width of the depletion layer to extend to the channel part is suppressed, dependence upon the voltage VDS (channel length modulation) of the drain and source current IDS is suppressed, and the imperfect transfer efficiency alphaD can be improved sharply. Moreover, sources and drains of the two FET's connected in cascade connection are coupled with an N type layer to attain reduction of diffusion resistance. When the device is formed in a multistage type by this constitution to make the FET's to be the fittest, the imperfect transfer efficiency alphaj depending upon a time constant according to ON resistance and the electric charge accumulation capacity of the FET is not also aggravated, and reduction of the driving voltage and enhancement of the frequency characteristic can be attained together.