Incomplete transfer in charge-transfer devices

The authors present a general analysis of incomplete charge transfer in charge transfer devices. By using a lumped-charge model to characterize the dynamics of the charge transfer, they calculate α, the small-signal coefficient of incomplete transfer, in terms of single-device small-signal parameters. They show that three contributions to incomplete transfer are common to all charge-transfer shift registers: an intrinsic transfer rate contribution, an output conductance or feedback contribution, and a storage-capacitance modulation contribution. The analysis suggests that most relevant measurements necessary to characterize incomplete transfer can be made on a single cell of a shift register that has input and output diffusions. This allows transconductance etc., to be measured on a small-signal basis as a function of transfer current, from which one can calculate transfer efficiencies. An analysis of the influence of interface states which may be important for some charge transfer devices, is also included.