Structure Dependence of Free-Charge Transfer in Charge-coupled Devices

A detailed numerical analysis of charge-coupled-device (CCD) charge transfer is described and discussed. The analysis is based on solving the transport equation with a time-dependent surface field calculated from the actual device configuration. Devices with different oxide thicknesses and devices with electrode gaps are examined. The total field is found to play an important role in charge transfer for all cases studied. The effective channel length is modulated by the net field present and is a function of time and electrode configuration. The transfer is found fastest and the effective channel length shortest when the charge is transferred from a region of low oxide capacitance into a region of high oxide capacitance. A low-capacitance electrode gap slows the charge transfer process.