Introduction to charge-coupled devices

The charge-coupled device (CCD) is essentially a shift register in which information is stored in the form of electrical charge packets in potential wells created in an MOS structure. Since varying amounts of charge can be introduced into the potential wells at one end of the CCD structure, to emerge after some delay at the other end, the CCD is capable of acting as both an analog and a digital shift register. The general operating principles of CCDs are described in terms of the basic properties of semiconductors in order to appreciate device capabilities and limitations. Attention is focused on charge storage and transfer, electrical and optical inputting of charge and charge sensing, factors governing maximum and minimum operating frequencies, transfer efficiency, and fundamental CCD fabrication techniques.