A Fundamental Comparison of Incomplete Charge Transfer in Charge Transfer Devices

Abstract

Using a small-signal analysis, we present a general comparison of the more important contributions to the incomplete transfer of charge in the following charge transfer devices: (i) the polyphase charge-coupled device and the IGFET bucket-brigade shift register, where individual charge transfers are single-step processes, and (ii) the two-phase charge-coupled device, the conductively connected charge-coupled device, the tetrode bucket brigade, and the stepped-oxide bucket brigade, where individual charge transfers are two-step processes. A recently proposed lumped-charge-model approximation is made in order to estimate the time dependence of the transferred charge including both drift and diffusion. In this calculation we also include the effects associated with the injection of charge from a diffused source into the IGFET channel which modify the current-voltage behavior at low currents. Using this calculation of the time dependence of the transferred charge, the various contributions to incomplete transfer, including those due to trapping in the interface states, are derived and compared for each of the charge transfer devices of interest.