Charge-control method of charge-coupled device transfer analysis

An analysis of charge transfer based on the "charge-control" approach has been made for charge-coupled devices (CCD's). A general closed-form equation for the charge transfer efficiency has been obtained that includes the major mechanisms of 1) charge-gradient induced drift, 2) thermal diffusion, 3) an external fringing field, and 4) charge loss due to traps or recombination. When the charge loss and fringing field terms are neglected, the results are in close agreement with the numerical solutions by Strain and Schryer. With the fringing field term included, the closed-form solution compares well with the numerical results by Heller, Chang, and Lo. The effect of charge loss on the transfer efficiency is studied and the temperature dependence of the efficiency, including the temperature dependent surface mobility, is discussed. The effect of a "fat" zero on the diminution of a digital one is discussed with and without charge loss to surface states. It is believed that the charge-control approach not only simplifies the mathematics involved, but also provides practical charge-coupled device and circuit design guides.