Change Transfer in Charge Coupled Devices

Citation

Daimon-Hagihara, Yoshiaki (1975) Change Transfer in Charge Coupled Devices. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/vx9y-gb03. https://resolver.caltech.edu/CaltechTHESIS:03212022-225418687

Abstract

Theoretical analysis of the dynamics of charge transfer in charge coupled devices is central to the intelligent design and proper estimation of the usefulness of this new device concept. In this report, a detailed study of the electrostatics and dynamics of buried channel charge coupled devices (BCCDs) is presented. Both theoretical and experimental study of BCCD has been very difficult due to the additional complexity in the BCCU structure in contrast to the original simpler structure of surface charge coupled devices (SCCDs). And up to present, no comprehensive study of BCCD which includes the complete electrostatic and dynamic analysis of BCCD operations has been reported. It is the purpose of this thesis to assist physicists, device engineers, and applications engineers interested in BCCD by presenting all essential information on the buried channel CCDs in one place and in a comprehensive form so that the background laid on BCCD can be applied immediately to the case of the SCCD studies achieved in the past and also to the investigation of a future CCD structure.

The work reported in this thesis consists of three major contributions to the rapidly progressing CCD research and is described in the main text, Chapter 1, 4, and 5 of this thesis.

In Chapter 1 the relations between the electrostatic potential and the charge distribution in one dimensional structure for BCCD are analyzed in detail. An expression for the channel potential in terms of salient physical parameters is obtained by depletion approximation. And its implications on doping levels, and profiles; charge storage capacity; geometrical structure and gate voltages are discussed in detail to provide a useful reference and guide-work in design and analysis of buried channel CCDs. The results obtained numerically for the case of Gaussian doping profile are also presented and correlated with the uniform doping model. In Chapter 4 a detailed two dimensional electrostatic analysis of buried channel CCDs is presented. By a simple capacitance network model the two dimensional Poisson equation appropriate for the structure is reduced into a second order differential equation in a single spatial dimension. The resulting equation relates the signal charge and the minimum channel potential under all the relevant electrodes and interelectrode regions. A diffusion equation describing the charge transfer is coupled to this equation in order to incorporate the static model in dynamic charge transfer description. The results of a detailed numerical simulation of the charge transfer process in the resulting realistic model of a high density buried channel CCU remain to be studied in Chapter 5. It is shown that the limitations on the device performance due to incomplete free charge transfer are reduced considerably by powerful field-aided charge transfer. The procedure to estimate the significance of this reduction in terms of the charge remaining as a function of time is formulated analytically.

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